The black one, a 3 year old, is sired by a black horse too...and has a "pink" lip. Here he is:
The white mark just covers half lip, if you look at him from the other side you don't see it
I took a photo at his legs too, even though I didn't find them "strange" enough to relate them to any kind of sabino whatsoever..
Do you think that face markings have to do with any particular gene ?
My mare has no outstanding marks on her, just those little spots perhaps:
Pedigree - http://www.pedigreequery.com/arroyo2
And his sire is all black except for the 3 coronets. His half brother, the bay colt I mentioned, has no white at all (curiously he is sired by another black horse, a full brother this colt's dad
) .
sire's pedigree
http://www.pedigreequery.com/zumbel4
, he is as black, but not as good-looking, in my opinion. But his owner won't cover any mares for the "public", just his own. 
...Well, he misses it, your mare looks great 
He gets up from the floor on a single jump, but walking is another issue !!
