The dog on the right is a cross between a low content wolf dog and a Labrador. The dog on the left is his son, produced through mating with a black Labrador mix.
Here is the low content wolfdog with his grandson and “daughter-in-law.”
My guess is the majority of the litter were black, but this one wasn’t. There also had to be a gene for the black mask in the Labrador mix mother.
NB: I use the term “wolfdog,” rather than wolf hybrid. Dogs and wolves are part of the same species, Canis lupus, and can’t technically be hybrids. However, crosses between dogs and coyotes and crosses between wolves and coyote would be hybrids.