“Baby daddy” is claiming he needs my daughters social for insurance paperwork ?

My baby’s father and I are not together. My daughter is 8 months old& she is under her dads insurance but she lives with me & is taken care of by me. He sees her on his days & that’s it. I’ve never given him her social security number or a copy of her birth certificate. He can get a copy if he needs it. Anyway he says he’s filling out insurance paperwork and needs her social security number for it. I’m not sure how that works but it seems odd that he needs it now all of a sudden when she’s been on his insurance just fine up until now. Does anyone know if he actually needs it ? I don’t want to give it to him unless it’s necessary