So yesterday I was playing normally and I thought by myself that can hybrids be made? I tried basicly biting, but that wasn't working. Anyways, if you use cheats, you can make this hybrid-thingythang happen!
So first of all, you have to create an alien, or then find one and move him/her into your house. You won't need a vampire to do this hybrid-thingythang.
Now, when controlling this alien that you are going to make hybrid, open up the cheatbox (ctrl + shift + C) and type in: traits.equip_trait trait_OccultVampire
This swaps your alien instantly into a vampire! Now, lets make few simple things clear. You can't make (or atleast I couldn't) a dark form or a disguise. On my case, when I tried to use dark form/disguise, it spinned around and gave me the original form of my alien. But now you can be recognized as alien and as vampire. Also, you CAN USE all alien powers AND vampire powers!
And with all of my own research there is NO WAY you could make hybrids naturally. I hope this was helpful thing you found useful.