John, only child of Francis II and his first wife Margaret of Brittany, was born in June, 1463 and died later that year. WHat if he had survived? With a male heir, would Francis II of Brittany consider marrying again, if so, and Anne of Brittany is still born, how does this influence politics of the region and France? With Francis having a male heir, Anne becomes a marginally less attractive prospect for a french marriage would it not? Who might John marry, what might he become under his father?
If John of Brittany had survived, I can see the Charles VIII of France/Margaret of Austria match going through, along with the Anne of Brittany/Maximilian of Austria match. With those matches, I can see more Austrian kids running around and maybe a longer running line from Charles VIII of France, although the Orleans line might still end up on the throne.
Speaking of Louis, Duke of Orleans, his bride might end up the Duchess of Brittany instead of of Duchess of Orleans. If that happens, then it probably won't be until 1505 for our Duke to remarry and have an heir. But most likely Joan and Louis are still a match and John of Brittany would most likely marry a Frenchwoman, maybe Anne d'Orleans.
An idea:
Francis II, Duke of Brittany (b.1433: d.1488) m. Margaret of Brittany (b.1443: d.1469) (a), Margaret of Foix (b.1449: d.1486) (a)
1a) John VII, Duke of Brittany (b.1463) m. Anne d'Orléans (b.1464: d.1491) (a), Françoise of Luxembourg (b.1470: d.1523) (b)
1a) Margaret of Brittany (b.1488)
2b) Joan of Brittany (b.1493)
3b) Charles of Brittany (b.1497: d.1500)
4b) Francis, Count of Montfort (b.1499)
2b) Anne of Brittany (b.1477: d.1514) m. Maximilian I, Holy Roman Emperor (b.1459: d.1519) (a)
1a) Charles of Austria (b.1494: d.1498)
2a) Miscarriage (c.1496)
3a) Francis of Austria (b.1497)
4a) Eleanor of Austria (b.1500)
5a) Stillborn Boy (c.1504)
6a) Barbara of Austria (b.1507: d.1507)
3b) Isabeau of Brittany (b.1478: d.1490)
Charles VIII of France (b.1470: d.1498) m. Margaret of Austria (b.1480: d.1530) (a)
1a) Charles IX of France (b.1496)
2a) Francis, Duke of Anjou (b.1498: d.1500)