Quote Nita Lou: I thought I remembered Alexis was raped by a older man? If so what about Starvos? Alexis and Nicholas have a very close bond... could be brother and sister? Just a thought or a possibility IMO. I could be in left field beyond the fence. Have wondered why Alexis has never told Sam about her papa, very strange she's kept it secret.
If Stavros raped his half-sister, Alexis, it would be incest, and I sincerely hope the writers don't go there. Also, since Alexis and Stavros have the same father, Mikkos, Nikolas can't be her brother. I'm guessing Nikolas was mostly left on his own growing up and Alexis was the one who was there for him and cared about him, which is why they are so close.
I don't believe Robert Scorpio is Sam's father either. Alexis knows Robert and has never acted strangely, i.e., like she has something to hide, around Robin.
I think Sam's father is someone we have yet to see on screen because Alexis has never gone "crazy" (for a better word) when she has seen any of the men mentioned in this and the other threads about this subject. I am going to be very happy when the identity of Sam's father is finally revealed. Hopefully, he will come to PC and Alexis will fall in love with him all over again. Maybe Sam's father will be the man she has been waiting (and kind of pining) for all these years.