M!Claude (most likely named Charles or Louis, let's say Charles) would most likely be the one to marry Mary Tudor, who is about 2 an a half years older than him. Renee of France is going to marry Francis, Count of Angouleme, to ensure that, if Charles dies too young or without issue, then France keeps Brittany. If he does marry Mary Tudor, then they might have similar issues to Mary and Charles Brandon OTL, with only female children surviving to adulthood. That, once again, separates Brittany from France.
One possible timeline is:
1499: Charles, Dauphin of France is born.
1510: Renee of France is born.
1514: Anne of Brittany dies, leaving Charles as Duke of Brittany. The Dauphin marries Princess Mary of England.
1515: Louis of France is born to the Dauphin.
1516: Louis XII of France remarries to the Queen Dowager of Aragon, Germaine de Foix. Anne of France is born to the Dauphin.
1517: Louis XII dies, leaving a pregnant Germaine de Foix as Queen Dowager. The Dauphin ascends to the throne as Charles IX of France. The posthumous daughter of Louis XII is born and named Claude of France.
1518: Elisabeth of France is born to the King of France.
1519: Charles of France is born to the King of France.
1521: Charles IX of France begins a war for Milan.
1523: Francis, Count of Angouleme marries Renee of France. Charlotte of France is born to the King of France.
1524: Louis of France, the Dauphin, dies. Charles of France, Duke of Orleans, becomes the Dauphin.
1525: Francis of France, Duke of Orleans is born. He dies later that year.
1526: The war for Milan ends as Charles IX of France is captured by Charles V, Holy Roman Emperor. As part of his release, his son Charles is betrothed to the Emperor's niece Dorothea of Denmark.
1530: Anne of France marries James V of France.
1531: Charles, the Dauphin, dies. Later in the year, Charles IX of France dies. Anne of France returns to France to claim the Duchy of Brittany. Francis, Count of Angouleme becomes Francis I of France.
Louis XII of France (b.1462: d.1517) m. Joan of France (b.1464: d.1505) (a) -annulled 1498-, Anne, Duchess of Brittany (b.1477: d.1514) (b), Germaine de Foix (b.1488: d.1538) (c)
1b) Charles IX of France (b.1499: d.1531) m. Mary Tudor of England (b.1496: d.1533) (a)
1a) Louis, Dauphin of France (b.1515: d.1524)
2a) Anne of France, Duchess of Brittany (b.1516: d.1534) m. James V of Scotland (b.1512) (a)
1a) Mary Stuart, Duchess of Brittany (b.1533)
2a) Margaret Stuart (b.1534: d.1535)
3a) Elisabeth of France (b.1518) m. Francis I, Duke of Nevers (b.1516: d.1561) (a)
1a) Francis II, Duke of Nevers (b.1539)
2a) Henri of Cleves (b.1541: d.1544)
3a) Anne of Cleves (b.1543)
4a) James of Cleves (b.1546)
5a) Marie of Cleves (b.1550)
4a) Charles, Dauphin of France (b.1519: d.1531) b. Dorothea of Denmark (b.1520: d.1580)
5a) Francis, Duke of Orleans (b.1525: d.1525)
2b) Stillborn Boy (c.1500)
3b) Stillborn Boy (c.1503)
4b) Miscarriage (c.1503)
5b) Miscarriage (c.1505)
6b) Stillborn Boy (c.1508)
7b) Miscarriage (c.1509)
8b) Renee of France (b.1510: d.1574) m. Francis I of France (b.1494: d.1547) (a)
1a) Louise de Valois (b.1527: d.1535)
2a) Francis II of France (b.1530)
3a) Margaret de Valois (b.1531: d.1533)
4a) Madeline de Valois (b.1534)
5a) Henri de Valois, Duke of Orleans (b.1535)
6a) Charlotte de Valois (b.1537: d.1544)
9b) Stillborn Boy (c.1512)
10c) Claude of France (b.1517) m. Ercole II d'Este, Duke of Ferrara (b.1508: d.1559) (a)
1a) Alfonso II, Duke of Ferrara (b.1538)
2a) Luigi d'Este (b.1540: d.1540)
3a) Maria d'Este (b.1541)
4a) Germaine d'Este (b.1544: d.1544)
5a) Ercole d'Este (1547)