Sorry is this is a partial duplicate. My hand slid on the keyboard, and I lost a long post just as I submitted it.
Briefly, I'm a direct descended of William Mitchell Clay and his only wife, Rebecca Cecil Clay. This is the William who shared Malinda's first two children, at least.
My autosomal DNA results found a match from my William to one of Milnda's children with no other shared names between us except William's ancestors. Science tells the truth...there is one strong case, so I'm checking similar matches to see if they are also unique, as well as which of the children matched.
If you've considered getting a DNA test to resolve specific questions/mysteries like whether they were all William's, please just get an autosomal test and forget the rest for now. Autosomal is like like looking for 7 (all her kids) needles in 10000 (or however many of William's descendents have tested Autosomal) haystacks. Y and mt are like looking for 0 needles in no haystacks, not applicable in this specific type of search.
Clay Cuz J.