Not my baby baby 

A baby that is not yours, but that you repeatedly have to tell people is not your baby because your ex girlfriend got pregnant by another guy so shortly after you broke up that everyone assumes it’s your bastard spawn no matter how many times you tell them it’s not.

I’m about to go on Maury and take a paternity test just to prove my ex’s new baby is a not my baby baby.

Not my baby baby by arnie123 June 8, 2018

That's not my baby to rock 

when a situation arises that is not your problem to address or remedy

Friend 1: (late at night) Tito just got dumped and needs a place to stay for a few nights.

Friend 2: That's not my baby to rock. Sucka.

Or

G/F: I didn't cum
B/F: That's not my baby to rock.

That's not my baby to rock by Red Mongoose March 6, 2011