Cosimo III De’Medici and his wife Marguerite Louise were not what you’d call good parents. Cosimo was reactionary, Marguerite Louise profligate and the marriage was unhappy. Amazingly, despite the dysfunction, they managed to have three children, of which the youngest, Gian Gastone, eventually inherited the title of Grand Duke of Tuscany at the age of 52, after his father had bankrupted the crown.
Gian Gastone continued the family tradition of unhappy marriages – of the 40 years of his marriage, he spent all of 10 months with his wife in Bohemia (where he met G.F. Handel, who went to Italy at Gian Gastone’s invitation and where Handel likely wrote the opera Rodrigo while in Florence, for Gian Gastone’s brother).
Though Gian Gastone reversed many of the reactionary policies of his father – he dissolved tax for the poor, stopped forced conversions of Jews and forbid public executions – he spent most of his time in bed. There, he was “entertained” by an entourage of street boys procured for him by one Guiliano Dami, boys who had sex with him and each other while he watched. He was reportedly grossly fat and a terrible drunk which in turn made him unfit to be in public.
He died in 1737, aged 66, supposedly well-loved by the Tuscans because of his reforms and despite Florence’s poverty.
There is a Gian Gastone de’Medici page on Wikipedia.