Southern mansion, bayou or swamp, manlike reptilian creatures, blackwater, reptilian baby

This book was set in the southern United States, possibly Louisiana or Florida, and is about a family who have been living in a large mansion surrounded by swamps for generations. In the swamps there are some manlike reptilian creatures, and the family living in the house has some kind of connection with them - manybe they interbred in the past? In one of the books, a young woman from the family gives birthh to a child that looked reptilian (or maybe twins, one reptilian and one normal), and I think it's father was one of the swamp creatures.

I am not sure when it was set, probably twentieth century but it had a timeless southern gothic feel to it. It was fantasy/horror and I remember the title being something like Blackwater, but maybe that was the name of the series (as I seem to remember reading more than one book), or the name of the house.

It was a library book and I remember the cover as having a plantation house/mansion surrounded by swamp and trees. I possibly read it in the 1980s but I am never much good at remembering when I read something.

In the past Googling never found these books, but after posting this, it occurred to me to do a tag search on "blackwater". One of the results that came up with was Michael McDowell's Blackwater. The tags looked right and I saw that it had been mentioned in the Gothic Literature board, so I asked over there and it is the series I remember.

Glad you found it! I can see why you remembered it!