Leonora was born in 1553 and spent her infancy very much in the background of Medici court life. As she passed out of childhood, it was evident that she possessed considerable charm. She was extremely pretty: her portraits show a fawn-like redhead, with huge dark eyes. Leonora was also extolled as gracious and genteel, charming and affable.

Isabella had not been especially interested in the infant Leonora, who at the age of five liked to attach herself to Isabella's younger sister Lucrezia. But she did later take the blossoming Leonora under her wing. Leonora saw Isabella as her role model and engaged in the same kinds of intellectual activities, music and sports.

Cosimo was also extremely fond of Leonora, to the extent that he had no desire to see her leave Florence, which was set to happen if her father Garzia found her a husband from elsewhere in Italy or Spain. So Cosimo decided to pre-empt Garzia by arranging, in 1568, a betrothal for Leonora to his son Pietro, who was a year younger than his fiancee. Cosimo was also attempting to ensure that his son would receive wife who had grown accustomed to his aberrations. Pietro had what would now be called learning difficulties: he was short-tempered and violent.

One result of the betrothal between Leonora and Pietro and realization that Leonora was in Florence to stay, was that the bond between Isabella and Leonora grew stronger. The pair became closer as Leonora reached maturity and she participated in her cousin's more adult-centric activities. Isabella had not been especially close to her own sisters, but Leonora was to become like a younger sister to her.

By September 1566, Joanna was able to announce that she was three months pregnant; in February 1567 she delivered a baby girl, who became yet another Eleonora to add to the household. Joanna produced two more girls in succesive years, but neither lived more than a few months. She had thus far disappointed Francesco in not bearing any sons. His feelings towards his daughters were limited. But although he was displeased at the lack of a male heir, at least his wife was having children, something that Isabella was not.

As the 1560s progressed, the issue of Isabella and the bearing of children was one clouded in mystery. Her ability to become pregnant had been proved by the miscarriages she had undergone in 1561 and 1562, but no concrete reports of pregnancy had been reported since that time.

In 1569 Pope Pius V elevated Cosimo to the rank of Grand Duke of Tuscany. This title, however, was not recognized by the Habsburg powers or by the other Italian duchies. To gratify the Pope, Cosimo in 1570 married Camilla Martelli, who had long been his mistress. Born into one of the most important families of the Florentine patricians, Camilla was the daughter of Antonio Martelli and Elisabetta Soderini. After the death of Cosimo's first wife Eleonora di Toledo and after the end of his relationship with Eleonora of Albizi, Camilla became Cosimo's lover despite being 26 years his junior.

Cosimo's children Francesco, Isabella and Ferdinando all reeled in disbelief at the news that their father had taken a new bride. After meeting with his father, Francesco reportedly left the room in tears, so humiliated was he that Cosimo,  Grand Duke of Tuscany, had married a woman from the less distinguished Florentine families.

While Isabella was prepared to accept that Camilla be a part of the family if it made her father happy, Joanna used her authority as a Habsburg princess to ensure she was denied a part in Medici public life. Unfortunately for Joanna, Cosimo marrying his mistress was to be a comparatively minor humiliation she was to suffer at the hands of the Medici men, and it was not long before she would come to regret isolating herself from her father-in-law.

It did not take very long for the scandal Camilla Martelli had generated to die down, both in Florence and beyond. Cosimo lived very quitely with his new wife, so it was fairly hard for outrage and gossip to be generated by a woman who was so rarely seen in public. Moreover, as 1570 wore on, there was a far more sinister figure than Cosimo's blonde bride dominating the minds of the Catholic heads of state. They were increasingly preoccupied with the goal of annihilating the looming menance of the Islamic infidel.

The Battle of Lepanto took place on 7 October 1571 when a fleet of the Holy League, a coalition of southern European Catholic maritime states, decisively defeated the main fleet of the Ottoman Empire in five hours of fighting on the northern edge of the Gulf of Corinth, off western Greece. The Ottoman forces sailing from their naval station in Lepanto met the Holy League forces, which had come from Messina, Sicily, where they had previously gathered. It was the first major Ottoman naval defeat since the fifteenth century, and a huge blow to that empire's prestige. It prevented the Ottoman Empire expanding further along the European side of the Mediterranean.

The struggles against the Ottomans continued, although they would be moved to land with the so-called Long Turkish War, begun in 1594 in the Hungarian border lands.

As preparations for Lepanto got under way, Isabella readied for an event of her own. This was the first time in her life Isabella had carried a pregnancy for more than a few weeks and she became appalled by the changes in her body. In 1571, Isabella's first child was born, a girl named Francesca Eleonora, for both Paolo and Isabella's mothers, but who was immediately called 'Nora' by her own mother.

For a woman who had been so ambivalent about pregnancy and children for so long, the instantaneous bond Isabella had with Nora was notable. She gave birth at the Baroncelli villa outside of the city and although a nurse would have fed the child, Isabella remained with her daughter in the countryside. On 13 September 1572 Isabella finally gave birth to a son, named Virginio.

 

Bianca Cappello was born in 1548, the daughter of Bartolomeo Cappello and Pellegrina Morosini, from one of the richest and noblest Venetian families, and was noted for her great beauty. At the age of fifteen she fell in love with Pietro Bonaventura, a young Florentine clerk in the banking firm of Salviati, and in 1563 escaped with him to Florence. In spite of the birth of a daughter, Pellegrina, her family wanted her back in Venice, and there was the fear that they might abduct her, incarcerate her or even kill her for besmirching the Cappello honour. Pietro, whose uncle back in Venice had been imprisoned in retaliation, had to go about Florence carefully for fear of assassination. With the romance dwindling, Bianca was to prove receptive to outside offers.

​Whatever were the circumstances of the meeting, one thing is certain: Bianca proved to be the only human being to succeed in arousing in Francesco the kind of obsessive devotion he had previously demonstrated only towards the study of chemistry and alchemy.

Although already married, Francesco seduced Bianca and gave her jewels, money and other presents. Bianca's husband was given court employment and consoled himself with other ladies. Brazenly, she made overtures of friendship to a clueless Joanna and, more remarkably, was successful in her attempts. It is difficult to understand how Joanna could not see what was so obvious to everybody else around her. However, the Habsburg princess's obsession with protocol meant she would not countenance being approached uninvited with such news by an inferior at court, and her rather limited Italian meant she did not pick up easily the gossip around her. When Joanna was told who Bianca really was, the revelation served to make her exceedingly unhappy. Her misery had been exacerbated by having gone to Cosimo to protest at Bianca's place at court and being met with little sympathy by the grand duke.

In August 1572 Pietro Buonaventura was murdered in the streets of Florence in consequence of some amorous intrigue, though it is possible that Isabella was involved. She calculated that Bianca as a widow was a much more vulnerable and potentially malleable creature, even as a prince's mistress, than she was a married one. That she had a legal husband was what had largely precluded her Venetian relatives from forcing her back to Venice. Isabella was sure that the potential isolation she faced now would make Bianca Cappello grateful for any prtoection Isabella might offer her.

​Despite Isabella's inability to neutralize Bianca, the period following the birth of her son Virginio was in many ways a very good time for the Medici princess. She continued to play an active role in the lives of her children. They were with her constantly and she spent far more time with them than her own mother had with her. Nora and Virginio's development delighted and fascinated her. In fact, they revealed what would otherwise be a hidden interest and talent of Isabella's, painting.

Early in 1573, Cosimo began to ail; he suffered from lenghty periods of partial paralysis. Mercifully, for someone who had lived with such vigour and energy, the Grand Duke of Tuscany was spared too prolonged an existence in such a state. His health deteriorated further in early April 1572, and towards the end of the month it was public knowledge that his death was imminent.

Francesco was summoned and arrived an hour later, where he carried out his first order of business as the new ruler of Tuscany. Camilla was forced to retire to the Florentine convent of Murate, a strict and severe institution. She was later moved to the convent of Santa Monica. She was allowed to leave the convent only to attend the wedding of her daughter Virginia, on 6 February 1586, with Cesare d'Este, himself the natural son of Alfonso I d'Este, Duke of Ferrara.

In the wake of Cosimo's death, all of Florence was keen to learn how he had distributed the Medici inheritance. The problem was, Cosimo's will had never been formalized, and it was in Francesco's power to carry out Cosimo's wishes as he himself, and not his father, saw fit. Ownership of the Baroncelli villa was in Isabella's name. It was her autonomous possession, so that property should not be contested by Francesco, however irritated he might be that his sister had secured it in the first place. However, Isabella was greatly concerned about her children's welfare and financial future. The Medici had no legal obligation to Nora and Virginio, who bore the name of Orsini and were their father Paolo Giordano's fiscal responsibility, even though they lived in Florence.

Isabella was not the only woman at the Medici court for whom Cosimo's death had brought anxiety, if not downright mysery. Camilla Martelli railed futilely against convent captivity, and Joanna was more tortured than ever before by her humiliation at the hands of Bianca. Isabella's cousin Leonora, married to her brother Pietro, was unhappy too. Cosimo had arranged the marriage in part to keep the charming Leonora in Florence. But he had also perhaps hoped that a bride who had known Pietro since childhood might help with the mental problems he seemed to be facing. An indication of his disturbance occured on the occasion of the official consummation of Pietro and Leonora's marriage.

Given that Pietro was less than physically prepossessing, while Leonora was the acknoweledged young beauty of the Medici court, such unwilligness on Pietro's part to have sexual intercourse with his wife could only be regarded as strange. Pietro's activities with other women are documented, so he clearly had his own reasons for his aversion to Leonora. Nonetheless, in early 1573, Leonora did give birth to a son, whom they named Cosimo and who became known as 'Cosimino'.

Just prior to the birth of his son, Pietro had been appointed General of the Seas of Tuscany, so he was given the naval career that would have been his elder brother Garzia's but for his death in 1562. Pietro embarked on missions that took him away from Florence. During these periods, Leonora spent increasing amounts of time in the company of Isabella, and while Isabella was the chief hostess to her group, Leonora sat at her right hand, praised and admired by those who visited. It was at Isabella's house where Leonora's troubles began to escalate. There was astonishing amount of temptation for a lonely girl in the presence of the array of sympathetic males assembled there, from the pretty pageboys through to their older cavalier brothers. Unlike her husband, they wanted her, to play with her, flirt with her, to go wherever she was prepared to go and willing to listen to whatever she had to say.

Paolo Giordano decided, at the end of May 1576, that he would come to Florence. He took his time getting there and did not appear until the first week of July. If Isabella's June was spent in gloomy contemplation of her husband's imminent arrival to Florence, then her cousin Leonora's was no less troubled. She had had bouts of illness in February and April, and, on 3 June, it was reported that she was very ill from incidents and many doctors say that they were doubtful that she was ill naturally. Florence, then, had its suspicions that the princess was being poisoned.