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#1 Old 17th Oct 2025 at 2:16 PM
Default Custom skins not being passed on genetically?
Hi! I'm having a problem with my sims genetics, specifically regarding custom skins, and I can't figure out why it's happening.

For context I am using pooklets rehash defaults for S1,2,3 and 4, as well as the geneticised additions that give more skins around the base four. These seem to work fine and my sims are getting all correct skins within the ranges, nothing weird there.

HOWEVER, I also have a few custom fantasy skins, which I am using alongside a multi-pt mod to create more varied aliens. I have followed a tutorial to make sure these skins aren't geneticised in the skin range, or generate on townies, and this also seems to work. I simply swapped out the PT's dna so that each one has a different funky skintone (I have a pink one, and blue one and a dark black one), though I left the original pt unchanged so his offspring still get the base alien skin.

My alien abduction children are coming out perfectly fine, with the correct skintones and features, but I'm having a problem with THEIR offspring specifically. When my hybrid alien sims reproduce with a sim with regular skintone, the child is 100 percent inheriting the regular skintones, not even carrying the alien skin as recessive. This is also applying to sims with the base alien skintone, not just the customs.

(I'm new to mts so I hope I have inserted these screenshots correctly)
[IMG][/IMG]

Looking in SimPE, my hybrid has inherited the alien skintone from pt, and S2 from her other parent. She displays the alien skin.

[IMG][/IMG]

Her partner, a townie, has S3.

[IMG][/IMG]

Their child inherits the skintone range S2 (from the hybrid's recessive) and S3 (from the townie). He displays S3. He doesn't have the alien skin as recessive.

I know that sims genetics are a luck of the draw, but this has happened with every hybrid offspring in my town so far. I have quit without saving and rerolled births too many times to count and the children are just not displaying my custom skintones or the alien skintone! Every other feature (eyes, hair, face) is mixing fine, they are not clones of one parent, it's just the skintones.

I do have a theory, but I don't really understand it myself which is why I'm asking for help. In one case, a sim inherited both a normal skintone and an alien skintone in the "skintone range" fields (I stupidly do not have screenshots as I edited the dna of this sim so that he displayed the alien skin because I was getting fed up of the issue). I can remember that the sim inherited a base normal skin (S1,2,3 or 4) and the alien skin, but the displayed skintone was one of the additional pooklet ones. It is my understanding that if a sim gets a geneticised skin and a non-genticised skin, it should be 50/50 which one they display, not a third different skintone. It looks to me then that the pooklet skins I have downloaded are interfering with the inheritance of non-geneticised skins, but of course I don't want to delete these if I can avoid it as many sims in my hood have already generated with them and that is a lot of work.

I hope that I'm just missing something and it's a simple fix. Any advice would be great!
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Mad Poster
#2 Old 17th Oct 2025 at 2:41 PM
It's just bad luck. From a hybrid and a normal sim, the baby has a 50% chance to inherit the alien skintone at all, and then, even if they do inherit the alien skintone, another 50% chance to display that one or the normal skintone. So it's only a 25% chance that they will be born displaying the alien skintone.

If a baby inherited a normal skintone and an alien skintone and then displayed a different normal skintone, that means you probably have two normal skintones geneticized with the same genetic value. This can happen if you have a non-default skintone that's geneticized with the same value as one of the four default skintones, which I believe are 0.1, 0.3, 0.6 and 0.9.
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Original Poster
#3 Old 17th Oct 2025 at 3:11 PM
Quote: Originally posted by kestrellyn
It's just bad luck. From a hybrid and a normal sim, the baby has a 50% chance to inherit the alien skintone at all, and then, even if they do inherit the alien skintone, another 50% chance to display that one or the normal skintone. So it's only a 25% chance that they will be born displaying the alien skintone.

If a baby inherited a normal skintone and an alien skintone and then displayed a different normal skintone, that means you probably have two normal skintones geneticized with the same genetic value. This can happen if you have a non-default skintone that's geneticized with the same value as one of the four default skintones, which I believe are 0.1, 0.3, 0.6 and 0.9.


This is both great and horrible news if it's just bad luck. My sims obviously just hate me haha. I will definitely double check the values of my skins, though! Thank you so much for a quick reply <3
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Original Poster
#4 Old 19th Oct 2025 at 4:17 PM Last edited by caramelzip5 : 19th Oct 2025 at 6:26 PM.
I'm so sorry I hope I'm allowed to reply add to my own thread, but I have investigated the genetic values of my skins and still don't understand this issue.



(I didn't save this sim, but I ran the simdna command before I quit and these ^^ were the results.)
The skintone range has a custom alien skin (32a etc) and another skin (6fbc etc). I recognise the 32a string as the custom black skin that I have given to one of my PTs, but I can't identify the other one. I have combed through all my skintones and I can't match it up.

This documents what I had mentioned earlier about a third skintone being displayed (in this case S2). The genetic value of S2 is 0.3, and none of my downloaded skins share that value, so I don't see why this is happening. The only thing I can think is that my default replacement for S2 has the 6fbc value but I can't seem to access the skinxml file since it's a default replacement, so I'm not sure how to verify if this is the case. Sorry again if I'm just being dumb lol!
Screenshots
Mad Poster
#5 Old 19th Oct 2025 at 11:16 PM
That means your custom skintone must actually have a genetic value.
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Original Poster
#6 Old 21st Oct 2025 at 1:41 PM
Quote: Originally posted by kestrellyn
That means your custom skintone must actually have a genetic value.


I can assure you it does not. None of my custom alien skins have genetic values, I made sure to follow a tutorial when I downloaded them and have since double checked all of them. I have managed to fix this issue now by changing the mystery skintone in the parent's dna to another one, then the 50/50 started working so I'm pretty confident that skintone was the problem.
Mad Poster
#7 Old 21st Oct 2025 at 1:56 PM
Yes, like I said, for that to happen, one or both of those skintones has a genetic value.
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Original Poster
#8 Old 8th Nov 2025 at 12:18 AM
Okay I figured it out. These sims had inherited skintones from a set that I previously used. I guess I didn't think about it when I switched them out for the pooklet set (oops) so their offspring were inheriting a string of numbers that doesn't correspond to a skintone anymore, hence displaying S2 instead. I'm lucky that I have a file of mods/cc I don't use anyone on my desktop (commitment issues, what if I need them again?!) so I was able to comb through the skintones and find the associated xmls. A stupidly simple problem haha

Hope this helps anyone who has the same problem!
Mad Poster
#9 Old 8th Nov 2025 at 4:02 AM
That's why when you give information like "this genetic code corresponds to this custom skintone" it's important to make sure that it's actually correct information. If you give incorrect information about what is happening in your game, it makes it hard for people to help you.
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