Babies relationship with parents at birth...

Have any of you found this odd?

In a "normal" go of Sims, my babies are born with about a 40% relationship with each parent. However, I am finding that very often (each baby in my current family but it has also happened in the past) is being born with only a relationship to one parent (the Dad in my current case).
I find this super lame, if anything the baby should automatically have a relationship with the mother!
Is this just a glitch that comes up, or does the game have some weird algorithm for making kids like one parent over the other (if that's the case, this poor mommy)?

Don't know why its only one parent should be both and its the same when you create in C.A.S Mother/Farther and you do a child/teen then when you start the game the friendship is all ways at 40%

As another piece to the puzzle, when the baby ages to a child, they have to introduce themselves to the parent that didn't have the starting relationship.
So my mother sim Rose... her son Jr. was born with 40% to his Dad and nothing to Rose. When he aged to a child, though both relationships were at 100% he had to "FRIENDLY INTRODUCTION" to his own Momma before they could interact any other way.

Scratches head Hmm! sounds like a glitch or bug now

Grrr, it's probably a mod issue then. But I will deal with it because I love the few mods I'm using hahahah