Half vampire half mermaid hybrid

@mistychristy24 

There are no hybrid mermaids and vampires in the game out of the box.  While one parent can be a vampire and the other a mermaid, sims born in game of such a union are one or the other.  They will either be a vampire or mermaid (and in rare cases, a human) and not have any traits, powers or weaknesses of the other.  Reading the vampire lore books doesn't bestow anything other than knowledge really for sims other than vampires.  To get sun resistance for a vampire, you have to build their powers to earn the perk which gives sun resistance.  

But if you are getting mermaid children which are getting that buff or the burning effect and motive drain on the sim when out in the sun, then that might be a bug as it shouldn't be happening. 

Hope this helps.

@Gagea25 

Interesting.  Then the problem hasn't been really fixed if it can still happen.  Fortunately for me, I haven't gotten another.  I did have one way back when Vampires was new.  It was a Vampire/Alien from an abduction pregnancy.  The sim was fine until she aged up to teen and became really glitched especially in CAS.  I finally had to delete her because of the problems with her.  Otherwise, I haven't had it happen again.  But tbh, I tend to make my couples either both the same occult or an occult and a human, not two different occults.  But I have had occults get abducted and come back pregnant a few times.  Every time though, the child was fully one or the other.  Most of those ended up as the occult rather than the alien.

I've had a number of alien/human hybrids though where the child gets the alien skin tone and has a few alien powers.  Those haven't given me any problems.  

@mistychristy24 There aren't supposed to be any hybrid occult Sims in the game, so these Sims probably won't be able to become vampires again if they are still mermaids. They should be able to become vampires again if you cure the mermaid condition. 

@mistychristy24 

They keep trying to patch hybrids out, which is a shame. I use a mod that makes the needs panel and perks interface less buggy.

Your only option is probably a bar and the Sun Reversal Cocktail. I always send my vampires to Uni with the pop-up bar, plasma fruit, and garlic so they can have that drink before class. You have to regularly make more, so…