Considering he had coke dick for much of the last 30 years, and she has none of his qualities, my guess there might be more than meets the eye.
It's possible, but I suspect for maybe other reasons. His cocaine problems supposedly didn't start until around '95 - a few years after he and Gladys split over him allegedly nailing Darcy Lapier. Darcy & VD later married and had a kid together.
Anyway, it wouldn't surprise me if Gladys had her own thing on the side, too; that's why I can easily believe Bree could have a different father. Gladys was such a babydoll! Regardless, the son she had with JC looks remarkably like him, but the daughter looks like pure Gladys, and that's a very, VERY GOOD THING!!