DeGrasse

So one of the family stories is that we are somehow descended from Admiral DeGrasse. I just read the other day that his son may not have had any surviving sons. So then how would we be descended from him and have that name. I'm not ruling out the fact that maybe a son was missed somewhere, you never know when reading stuff with no source information. I suppose we could be descended from a daughter that gave her child the name and not her married name. Hmm... It sure would help if I could find information on Wilfred and his father. There's always the brought here by aliens theory!