i'll just give you the starting point, however.

in genesis, it says that one of the worst things about the fallen angels was that they were "taking human wives" and you know what their offspring were.

the catholic church, who compiled the book that is today called the christian bible, actively attempted to wipe the book of enoch from existence, because, although it is pretty clear in genesis that angels and humans could interbreed, enoch leaves you with no doubt in your mind that is because they are physical (not just created) beings. biologically, human, to use science words.