I tried to breed this unicorn stallion Caramel; http://beastkeeper.com/lot/2/8890 to my mare Northern Shan; http://beastkeeper.com/pet/56835 both times I got Breeding is impossible! What is the matter with the breeding? I'd like to breed her to a double cream stallion to get a cremello with better stats than she has. Tried it again with a different stallion & it's still impossible, she's at 3 of 17 breedings, has 10/10 energy & has no effects. Just managed to breed her to 1 of my stallions but would still like to breed her to an outside stallion.

This stallion has reached his breeding limit, you can't breed with him until his owner increases his strength to get more breedings.

OK, but would that apply to all the stallions I tried breeding to? And how can you tell if the stallion doesn't have any breedings left?

Not sure what you mean in the first question. You can breed with any stallion who has at least one unused breeding. Concerning second, just check the stallion's profile if you have problems breeding with him. The breeding limit is visible to all players, not only to the pet's owner.