@Kattodesu Spirit sired at least 2 offspring which are currently considered canon. Spirit Jr. from Netflix's Spirit: Riding Free and the upcoming Spirit Untamed film, and a filly who appears to be almost identical to Spirit Jr. who was introduced in a book called Lucky & The Mustangs of Miradero(?).

The silhouette next to the her is most likely her mate and wouldn't be related to Spirit by blood. Their foal is a solid buckskin (no blaze) and would be the original Spirit's grand-daughter.

It's possible Spirit may have sired many more foals than that, as real life mustangs in the wild will breed several mares every year. But as it stands right now, only Spirit Jr. and his sister are part of the official canon to Dreamworks.

Did spirit sire three other foals?