User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-24205801-20121118053718/@comment-3146930-20121121003329

Pretty much any demigod is related to another demigod in some way. I mean all the Olympian gods were either born from Kronos or were born from Hera and Zeus (with few exceptions). While Aphrodite was born from Ouronus however, he was Kronos' father so she is still related to the gods. So Hephaestus pretty much married his Great Aunt while Ares is also dating his Great Aunt. This is why in the books they explain that gods don't have DNA and as long as you aren't dating someone with the same godly parent, you are in the clear