Leonardo da Vinci: wedding planner, and Isabella d'Este
One of those little known things about Leonardo da Vinci is that at age 40 he was hired as a wedding planner. While it confirms that he was a man of many talents, it also shows a man who enjoyed life and it contradicts the popular image of him as an aging, serious genius focused only on his painting. Indeed, one of the reasons so many of his paintings were never finished is that he lost interest when there were other things to distract him which were more fun - like organizing weddings.
Milan
Leonardo spent nearly two decades of his life in Milan, from 1482 to 1499 (from age 30 till he was 47), under the patronage of Ludovico Sforza (Il Moro), the Duke of Milan. Leonardo's title for a while was Master of Feasts & Banquets and this meant creating elaborate spectacles - dances, masquerades and theatrical performances - where he chose the locations, the layout of the rooms, the set design, the costumes, and the visual and lighting effects. There are no Leonardo paintings of these spectacles, I'm sorry to say, so I've chosen one by Botticelli instead, based on a Decameron story:

These were wealthy families marrying into each other and everything was heavily political. One major wedding for Leonardo was in 1489, when Isabella of Aragon married Gian Galeazzoto Sforza. A second major wedding, in 1491, was even more significant: a double wedding between the Sforzas of Milan and the influential d'Este family of Ferrara. Leonardo's patron Ludovico Sforza married Beatrice d’Este (he was 38; she was 15); and Beatrice's younger brother Alfonso I d'Este married Anna Sforza, who was technically Ludovico's niece (he was 14; she was 15). Ludovico's wedding already had been delayed because of his preference for his mistress Cecilia Gallerani, whom Leonardo also painted (here). Leonardo painted most of these people during his time in Milan.
Things did not go well for the Sforzas. Beatrice was a warrior queen - she loved to shoot a crossbow - and she was a shrewd politician in her own right, but she was dead at 21 in childbirth in 1497. In 1499, the French invaded and after various battles, Ludovico was taken to France and kept in prison until his death in 1508. Leonardo fled when the French arrived, first to Mantua and then to Venice.
Mantua
The center of gravity in this story is not only Leonardo, but the older sister of Beatrice and Alfonso, Isabella d'Este. She had married Francesco II Gonzaga, the Marquis of Mantua by proxy in 1490, when she was 15. An intellectual in her own right, she was as important as Leonardo as a patron of the arts and fashion in Renaissance Italy and she had a long term friendship with Leonardo. The portrait shown up top is thought to be from 1499. In typical Leonardo fashion, he never finished it but it is surely more accurate than the flattering terracotta bust shown below, which is thought to be her.

This bust is by Gian Cristoforo Romano, who created a number of portraits and medals for Isabella in Mantua. It is dated around 1500 and probably it was once painted. The Kimbell Art Museum in Fort Worth, which holds the bust, identifies it as "probably representing Isabella d'Este," and that seems right. Below is a much later Titian painting commissioned by Isabella, idealizing herself as a young woman, since she does appear to have worried that her portraits were never flattering enough! (She was in her early Sixties by then).

Ferrara
Meanwhile, in Ferrara, Isabella's brother Alfonso had a series of affairs and contracted syphilis. His wife, Anna Sforza, seems to have preferred women and she refused to consummate her marriage for some time, or maybe the syphilis was off-putting, but again tragically she would die in childbirth in 1497, months after Beatrice in Milan.
Alfonso married again in 1501, this time to Cesare Borgia's sister, the infamous and extremely wealthy Lucrezia Borgia, now on her third husband. Things took a turn for the worse in 1503, when Lucrezia began a long term affair with Isabella's husband Francesco (whenever he visited Ferrara), deeply offending Isabella, although Isabella continued to have children with him. If Leonardo drew a portrait of Lucrezia, nothing survives, but I like this coin with her on it:

Leonardo meanwhile had landed in Florence by 1501, working for Cesare Borgia as a military engineer till the following year.
Who lasted the longest?
By 1519, Leonardo is dead. So are Francesco (Isabella's husband) from syphilis and Lucrezia (his lover), from childbirth. That leaves only Isabella's brother Alfonso who lived till 1534 - despite the syphilis - and Isabella herself who outlived them all; she died in 1539 aged 64. This is her coin:

It is the only confirmed portrait of Isabella because it has her name on it.
The painting below is said to be a print of Leonardo's portrait of Beatrice, but it resembles dozens of other paintings from around the same time, and is thought by some to be Anna Sforza, so who knows?
