Looking at Ivy, I can't imagine pit bull terrier but I have no idea what shelter people think they see and the photographers (bless 'em) are sometimes volunteers without the best lighting usually. Perhaps their dog has a heavier head and neck. Of course, some litters do have multiple sires .

But I do agree, due to similarities, if age is similar, they could be siblings - if there were siblings.

If you have contact info for the 'breeder' then perhaps you could ask them to follow up? Otherwise if you can, you or a friend who knows Ivy, could go look?