This summer different members of my family will be going in together on big a beach house. There's just one thing. "Heather" used to be married to my cousin, but after they split up, my cousin moved and Heather is still invited. She also is younger. The problem? I think she's hot.
Very very hot. Am I allowed to ask her out? It's really hard to be around her all weekend in bathing suits and beach clothes and share a bathroom. Is this too incesty a situation? Should I just not go?
Depends on what you call a "problem. There is no legal problem here. No biological one, and no moral one, either. There may be a slight social one, though — cousin marriage may be largely legal but it is still considered freakish most places.
Cousins actually have been coupling as long as there have been cousins; in the small bands and villages of our past there may have been no other choices available. Even brother/sister incest has had its proponents, although these are few and their most famous example, the Egyptian royal families, were remarkably weak and weedy specimens, not to mention all dead now. So we won't do that.
Ideally, we won't all hook up with our cousins, either. The occasional intramarriage is harmless, but for the race as a whole that good hybrid vigor seems a worthy goal. Mix it up, it's good for us! Historically, we have had a nearly universal incest taboo (for first-degree relatives, cousins are third degree and have generally been a gimme) for a reason. And not only have we historically frowned upon congress between first-degrees (people with whom you share half your genes), very few humans even seem to want to.
Does any of this have anything to do with you and your situation? Certainly not. There is no incest taboo in your case because there is no incest, period.
This is not to say that your ex-cousin-in-law will welcome your attentions, and her possible rejection, if any, will have nothing to do with incest taboos or the relative turn-on-itude of exogamy. She may just not like you that way. She may think you are old and creepy and shouldn't be looking at young women like that. You never know. Neither can I guarantee that your real relatives, who have welcomed this young woman into the bosom of the family, will not be somewhat disgusted by your behavior. These are risks one takes any time one approaches a potential partner, of course, and if you don't accept the risk of rejection you never get any partners at all. But most of the time when you go out on a limb and risk looking foolish, you're alone, or in the company of friends, who might rib you a bit and then drop it. Families, as anyone who has ever taken a summer vacation with theirs can attest, never drop anything. So proceed with caution, or go to Italy this year instead.
Got a question? E-mail Andrea at firstname.lastname@example.org