A vampire Sim and a mermaid Sim can have a baby together in The Sims 4, but the results are often glitchy and broken.
The Sims 4 does not support hybrids or cross-breeding.
If a mermaid and a vampire have a child, the child will not inherit traits from both parents. They are always either a mermaid or a glitchy vampire-mermaid hybrid, never a full vampire.
While gamers can technically create vampire-mermaid hybrids, these Sims will be buggy.
The vampire-mermaid hybrid children have invisible tails, try to swim through sand, and burn in the sun. When they age up and go swimming for the first time, they lose their bottom halves after getting out of the water, left with no tail or legs.
They are unable to access the vampire powers panel to spend points.
The Sims 4 Does Not Support Mixed Life States
Hybrid Sims are broken in The Sims 4 because the game does not support mixed life states. The best solution is to avoid creating hybrids. Broken Sims can lead to game file corruption and various glitches.
Creating hybrids causes issues because the game’s UI cannot handle mixed features. Gamers who tried to create vampire-mermaid hybrids found that the hybrids had abilities of both types, such as vampire energy and hydration needs.
However, the game did not show them as hybrids. The game UI would show them as mermaids without access to vampire points or powers.
In Create-A-Sim (CAS), you can only edit two forms, but hybrids have more than two forms, which confuses the game. Many players confirmed this issue.
You might pair a mermaid and a vampire, expecting their child to be either one or the other. Instead, you could end up with an unplayable hybrid. Everything might seem fine until the child becomes a teenager.
At that point, your Sim could develop their vampire form but still have mermaid traits. They would lack a hydration bar and have regular needs along with vampire energy, but no access to vampire upgrades.
The CAS UI can get really messy and glitchy at that point.
Mermaids vs. Vampires: Supernatural Abilities
Mermaids and vampires share some similarities. Both possess supernatural abilities. However, mermaids’ powers are not as extensive as vampires’.
One interesting mermaid ability is changing other Sims’ moods. Mermaids need to be mean to other Sims to replenish their status bar when others become stressed, uncomfortable, or confused.
A unique mermaid ability is the Summon Ocean Threat, which can lure Sims into the ocean and trap them underwater.
Similarly, vampires can influence other Sims’ moods and actions. The Vampiric Charm makes other Sims feel attracted to them.
The Command ability allows vampires to control other Sims, forcing them to perform various actions like cleaning, repairing objects, and interacting with others.
Long Story Short
While creating a vampire-mermaid hybrid might seem appealing, it is best to avoid it. The game does not support hybrids. Although it is possible to create them, these Sims will become unplayable once they reach their teenage years.