I'm not super educated in the omegaverse world and each author's omegaverse can have different rules. I was under the assumption that Beta's can't get omega's pregnant. But say they can get an omega pregnant I would assume only a beta or omega (probably a very small percentage of a child being omega, I think though) child is possible. Taehan is an alpha. But again, I'm not super educated in how the omegaverse world works completely and each author's world can work differently than others.
But after saying that, this has been confirmed by the author. Taehan has Omega & Alpha parents. This topic was talked about a lot when the raw chapter came out. And the translators I follow on Insta were quite clear about who was alpha and who was omega. Too, I think the author was trying to break stereotyping. That not all omegas are small and innocent looking and not all alphas are tall, strong, manly.
Is the omega dad the tall black haired one and is the short brown haired one a beta dad??