I have noted that aspect, via the Sersi wiki. Complicated can be fun.
That's great! It can be as complicated as you'd like. It'd be cool if there was a weird clash of customs, though. "But Dane, you're not an Eternal. You wouldn't be able to comprehend why I'm sleeping with those other Eternals." Or something. o_o
We can hash it out once you decide on your character and work things out with the GMs.