My very affectionate male cat suddenly won't let me pet him

Hi everyone I'm new here

Sable is a 2 year old fixed male cat who previously used to sleep with me every night. He grew up in a house with a lot of cats so when I moved into my own single apartment I brought in a female Persian stray.

They got along great would cuddle and clean each other.

The Persian just gave birth about 2 weeks ago and ever since then Sable has been giving her and the kittens space by staying outside more

But yesterday I went to pet him when he came inside and he shyed away against a wall like he didn't know who I was at all.

This cat used to follow me into campus while at college and wait for me outside of class now he acts like he doesn't know who I am.

What could it be? Just him getting older? Or is it the kittens?

I need help in scared he won't come back one day.

It could be that the mama cat is being protective and driving him away.  They change behavior after having kittens and will usually keep most other cats away from the babies.  It might help if you could confine her and the babies to one room and then see if you can get your boy inside again for some love and cuddles.  We all know that cats can communicate telepathically and so if she is telling him to keep his distance, then he is getting the message.  If he is shying away from you, perhaps your hands smell of her or the kittens.  You might try washing your hands before touching him, and also rubbing them with catnip.  In any case, you need to find a way to make him feel safe and welcome in his own home, and when the kittens are older, he may start enjoying them, but right now the whole process is upsetting him.