What is the name of your state? California
Here are the facts in the order they happened:
I had a vasectomy and am unable to have kids (easily).
My girlfriend's is 40 and wants kids ASAP.
Rather than break up, I encourage her to find a sperm donor.
She finds a friend (acquaintance, no prior relationship together) willing to donate sperm and impregnates herself with a "turkey baster". There is no legal agreement.
She learns she is pregnant.
We get married and buy a home.
Sperm donor decides he wants custody and sues.
She has the baby. I am listed as father on birth certificate.
We are happily married and raising the baby (now 2.5 months old).
Sperm donor was allowed a couple of brief visits in the hospital, but otherwise we have had no contact with him.
From brief conversations with him it seems peaceful resolution is highly unlikely.
Who has the better case for custody: husband or sperm donor?