ARGGGHHHH, hit the wrong key and deleted my post.
Okay, will try again. I don't know if this is of any interest to anyone but me, but I wanted to share it just in case.
First experiment
Astra is half and half, married to a full human, had a daugher (Megana).
With neither she nor her daughter could I hear their voices until they became teens, which was when they showed they had alien abilities.
Megana was married to a human, their offspring, Star, I was able to hear her voice and she had no alien abilities.
Second test
With Megana, I married her to a sim from another game and town where he was half and half. Their offspring, who I named Star, I was able to hear her voice. I figured that meant she would not have the alien abilities. Wrong, she had the alien abilities.
Star married a full human and with their son, Drago, I was able to hear his voice, yet at teen he also had alien abilities.
He married and their daughter, Kira, did not have alien abilites.
With the sim being half and half, that sim's offspring had alien abilities, but from there on, if mated with a human, no alien abilities.
However, if that sim is mated to a sim who has alien abilties (if a half and half), they should have two generations of alien offspring. I can only assume that if both were from second generation their offspring would have alien abilities but the next one wouldn't.
For me, I just like knowing, the wondering of "what if this is done", yet also to help if later on I decide I want to breed in some alien genes, yet not have my sim kidnapped. I can just take a sim from the saved bin and add him to the family.
Edited:
Was doing next experiment (mating of Megana and human which had in first two tests resulted in Star as full human), with plans to marry Star to half/half and see how far next generations went on alien powers.
That was shot all to pieces when Megana and human had Star but this time she HAD powers.
I can only assume that it is random on how many generations the alien abilities are passed on.
I had expected Astra to have a child (Megana) with alien abilities, but not for Megana to have a child with alien abilities. Megana would have been what, 25% of alien, so I had figured the programing was stopped there for passing on alien abilities.
Obviously, I was wrong.