I'm utterly convinced that Elle is Adam's daughter

You think the show is going to give us textual incest instead of subtextual one then? Because Adam did imply he had sex with her six years ago.

and that Claire is related to them too. So much blondeness!

Hm, like I said to W., I've seen the speculation that Meredith might be Elle's mother, making Elle Claire's older half-sister, but Meredith isn't old enough if Elle is 24. However, Meredith could be Adam's daughter. Hell, given that he had 400 years time, Adam could be the ancestor of each and everyone on this show.