No problem with the sex game with Aphrodite. There's so much incest going on on Mt. Olympus that it's practically given that if you mess around with a god there's a good chance they are related to you in some way. Also the gods are above things such as incest. They are above things such as what happens when you have kids with your relative (physical deformities and such). When you look at Olympus, it's probably better to look at the gods as a bunch of different people with no relations other than being gods.