According to Islam Mohammed is a direct blood descendant of Ishmael, Abraham's' oldest son. But I think this poses a problem with Islam. You see, all modern people trace their ancestry through Noah and his family. All other families were destroyed by the flood. So, at least as far as I know, and I could be wrong on this, that means Abraham's' family line was destroyed too. UNLESS if Noah is a direct blood descendant of Abraham. So, here is the problem, IF, and I do mean IF because I am not entirely certain about this, Abraham's family was destroyed in the flood, then that means Mohammed can not be a direct blood descendant of Abraham. IF he is not, then that means his claim to being a prophet becomes undone. I very uncertain about this, however.