Think my cat had inbred kittins?

Okay soo I got a kittin from a guy in my old nieghborhood she was indoor outdoor when I got her and remained that way. When I moved to my aparment I kept her and I guess as soon as I moved she got pregnat? Well she had them and she orginally had 4 but only 2 plain white ones made it, The others had weird legs they were deformed and the two white ones have too many toes like 7 & 6 toes Im thinking maybe she had mated with a family member? Could these deformed kittins mean that?