I agree, a reverse brindle can look black.
However, please encourage you mother and brother to spay/neuter asap, as well as your own boy and make sure the new owners of all the other puppies do the same.
Santina, owned by
Sky, Boxer, flashy fawn, docked and floppy, 7-24-09, CGC.
Happy, Puggle, 2-28-08, CGC.