We know Louis XIII and Anne of Austria's marriage wasn't a happy one and this impression is strenghtened by the fact it produced only two children : the future Louis XIV (1638-1714) and his brother Philip, Duke of Orléans (1640-1701). What is not taught in History lesson is that Anne suffered four miscariage before the birth of OTL Louis XIV.
My mind wandered on what would have been the consequences of the four stillborn child not having been stillborn. So, let's say they were not as our POD. Thus, Louis XIII and Anne of Austria have the following children :
1. Louis (born on December 1619)
2. Marie (born on March 14, 1622)
3. Elisabeth (born on 1626)
4. Philippe (born on April 1631)
5. Henri (born on September 5, 1638)
6. Charles (born on September 21, 1640)
Given that OTL Louis XIV lived up to 76 and his younger brother to 61, we can assume that those children will live up until the 1700s or around so.
The first and direct consequence of Anne of Austria bearing so many children would be that her regency following the death of Louis XIII in 1643 is butterflied away. The reason is that the heir to the throne (the ATL Louis XIV in this case) would be 24. Without Anne's Regency, Cardinal Mazarin's position might not be as important as it was, and the Fronde could be butterflied away.
Another consequence is that it will probably weaken the position of Gaston d'Orléans, younger brother of Louis XIII. OTL, Gaston was Louis' main opponent and his position as heir made him a strong opponent until OTL Louis XIV was born in 1638. With a son born as early as 1619, Gaston won't be much of nuisance. Without him, the Fronde des Princes is likely to be butterflied away.
What other consequences could there be?
Who would be the possible brides (or husbands for the girls) of those children?