She was only in her grandmother's care for a very short period of time. Her father died May 4 of 1519, and Alphonsina died less then a year after her only son, in February 1520.
Catherine seems to have had a lot of her grandmother in her. Alphonsina was the power behind her son. Raised at the court of Ferdinand I of Naples, she was a powerful and wealthy woman on her own. When her husband Pierro was sent into exile with the men of his family, she worked hard to have him returned. Pierro died in exile, but Lorenzo became the leader of Florence much in part due to his mother and her political intrigue. She served as his regent when he was out of Florence, and when he was there still held influence. She was quite popular. She left much of her fortune in the hands of her brother in law Pope Leo X as he was to look after her daughter and granddaughter.
Francis I sought for Catherine to be sent to France to be raised. Leo stepped in though and had other ideas. It was her paternal Aunt Clarice De Medici who ended up raising her. Clarice was married to Filippo Strozzi the younger. Clarice saw to Catherine's upbringing and education.
It wasn't until 1533 when she married Henry that she would go to France. Henry was a younger son but for all their extreme wealth and political power in Italy, the de Medicci's were commoners. It was considered a great match for Catherine by Pope Clement (Leo had died in 1521).
In 1536 she would become Dauphine, when her husband's older brother Francis died and Henry found himself heir.
She had ten children, seven of whom reached adulthood. She sadly out lived all but one son, Henry III.
-Frances: succeeded his father as Frances II. He was married to Mary Queen of Scots. He died at sixteen, less then 18 months after his father died.
-Elisabeth: married Philip II of Spain. She was the 3rd of his 4 wives, the second of whom had been Queen Mary of England.She gave him 2 daughters who reached adulthood.
-Claude: married Charles III, Duke of Lorraine. One of her daughters was married to Ferdinando, Grand Duke of Tuscanny. Ferdinando de Medici belonged to the Tuscan branch of the family but related to both. Giovanni di Bicci de' Medici, founder of the Medici bank had three sons. The Florentine branch (Catherine's side) was from his son Cosimo. The Tuscan branch from his son Lorenzo (Ferdinando's). But Ferdinando's father was related to both branches. His maternal grandmother Lucrezia was the sister of Catherine's grandfather Piero.
-Louis: died in infancy
-Charles: became Charles IX. He married Elizabeth of Austria. Their only child was a daughter Marie Elisabeth who died at age 6.
-Henry: became Henry III after the death of Charles. The only child to outlive his mother. He married Louise of Lorraine. He was succeeded by his brother in law Henry of Navarre.
-Margaret: was married to Henry of Navarre but their marriage was annulled. Her husband succeeded as Henry IV of France after her brother was assassinated. Henry would later marry Marie de Medici. Marie was the daughter of Francesco I de Medici. Francesco was the older brother of Ferdinando (the son in law of Claude).
-Francis/Hercules: he changed his name at confirmation to Frances, after the death of his older brother. Duke of Anjou. He was known for his courting of Elizabeth I.
-Victoria: a twin, died in infancy. her twin died in the womb but Victoria was born alive but survived a month. The birth almost killed Catherine, and the king was advised not to get Catherine pregnant again. After this he spent his time with Diane instead.
-Joan: the stillborn twin of Victoria
