Unfortunately, the game developers forgot to include hybrid genetics. So, what I do is use the cheat codes. Ctrl Shift C Testingcheats On Enter Testingcheats True
I give some of my Sims all four Occults with the proper order:
1. Traits.Equip_Trait Trait_OccultVampire
Stats.Set_Stat RankedStatistic_Occult_VampireXP 1593
Press Enter Arrow Up to repeat for the Vampire Perks, then select the Strengths & Weaknesses.
2. Traits.Equip_Trait Trait_OccultAlien
3. Traits.Equip_Trait Trait_Occult_WitchOccult_BloodlineAncient
Stats.Set_Stat RankedStatistic_WitchOccult_WitchXP 2850
Press Enter Arrow Up to repeat for the Magic Perks, then select your desire Magic Powers.
4. Traits.Equip_Trait Trait_OccultMermaid.
And that is how you get a Quad Hybrid.
You can also just have two or three Occult traits in your sim.
These cheat codes aren't mods or mccs.