How can a gay man have a daughter?

How can gay people have kids without adopting them?
I told this gay guy " aren't you gay"? since he was having baby fever
He: gay people have kids lol I have daughter
Me= gay people shouldn't be allowed to adopt
He= My daughter is biologically my child, she’s not adopted lol.

so i'm very confused how can a gay man have kids without adopting them?

is he saying he was straight once and had kids but now he's gay?
How can a gay man have a daughter?
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