I'm so sorry you are experiencing such an uncomfortable situation 😔. It sounds like your husband is comparing the kids complexion to other quarter mixed children which I can understand, but please tell him that this is a normal thing. Plus when you say he is 50/50, is his dad black ?
And which kid is he worried about ? The second or the first?
He won't listen and won't hear it when you explain genetics or reason? What is he expecting you to do here? Unmake the baby?
That’s insane that your spouse is saying that. When my babe was a newborn, he looked complete Chinese. Now that some months has passed, he looks less and less Chinese and more like his dad. The point is 1) genetics can produce different looks in siblings 2) babies are still growing and can change and 3) don’t worry about what other people think. People will always have opinions. What if your kids were actually adopted? Why would that be an issue to other people? If you are around people that are that judgy and opinionated, they are not your people and not for you or your family.
The children look pretty similar outside of their complexion. He needs to chill especially if he has NO other reason to be suspicious about you cheating. That's a HUGE accusation.
My little boy doesn't look mixed at all. He has the same skin complexion and hair colour as my niece, who is white. My husbands mum is mixed Caribbean and white, and his dad is black African. My husband isn't dark himself, but his siblings are. I sometimes worry that people might think he's not our sons father, but you can see his features in him. My husband always says he doesn't care what others think, though, because we have a happy, healthy little boy who he knows he's the father to. I know I get looks when I tick mixed race on forms, and he walks in😂