I'm going to lock this as I'm not even sure if it was still an issue after the infant patch.
If you do still have issues with toddlers, please create a new thread.
My sims just had a baby and did not have to introduce themselves!
@MapleSimmer Neither of them had the Beloved trait so I think you're probably correct about that trait being connected to the issue. One thing I noticed is that both parents had a lot of friendship with the baby right after she was born. In the saves where the parents had the Beloved trait, there was very little friendship with the baby. Hopefully the devs can do something with this information. Perhaps the old bug that they fixed was somehow reintroduced at some point.
I'm also having this issue I noticed once I got the beloved trait no matter what interactions with babies in the game they don't gain any relationship with sims who have it. I used the code to remove the trait and my mother instantly became best friends with triplets after one interaction. They haven't aged yet but I am assuming that solves the issue. I'll report back if it doesn't. xD
