Ty and Rocky Blue are the result of a cuckold relationship. Look at them compared to their parents. They both have a lighter skin tone than both of their parents. So, it's very clear that the person that they think is their father is not really actually their father.
He's aware of that though. No one is going to be that ignorant willingly. Okay, maybe there are some people who are. But Curtis is a doctor, he's not that stupid, he would obviously have knowledge of genetics in some way and would know that they're not is. He knows that these children that are not biologically his.
But he's completely fine with it. He has absolutely no anger towards his wife having sex with other men and getting pregnant by them. He is quite obviously a very busy doctor who has a lot to do, and with him being very busy he wouldn't be able to please his wife as frequently as he would want to, plus all the stress might affect his performance in bed. He also seems to be away frequently, which would lead to his wife getting lonely. She could use toys, but that's never the same as a really cock, the real touch that comes with having a real person fucking her. He was also frequently away on business trips, so there would be a lot of times that he wasn't there at all, so there would be times that even if he wanted to pleasure his wife, he wouldn't be there to do it, although the sex when he got back would have had to have been very wild, reclaiming his wife after some other man or multiple men even had been cumming inside of her.
He would have no issue with this if he was confident enough. He would be fine with his wife having another few men to help her when he was away. It's not for everyone but it would be for him. He would have no issue with someone else having his wife and pleasuring her.
He would want family. It would be ideal for him to be the father of the children, but maybe for various reasons he couldn't or didn't want to be the father, or maybe not. Maybe the time was never right to get her pregnant. Or maybe it just so happened that she got pregnant with someone else. Maybe they didn't care that someone else got her pregnant, just that they had children.
Maybe sometimes he liked to watch. Letting his wife get fucked by other men, being confident enough to let that happen, maybe sometimes he watched. Maybe he enjoyed seeing other men pleasuring her. He already was allowing her to fuck other men, why wouldn't he like watching sometimes. Of course, he wouldn't always be there, but he'd sometimes might like to sit beside them and just watch that other man fuck his wife and pleasure her. Seeing this strange man or maybe it was someone who they knew, either closely or vaguely, fucking his wife. Some other man making her feel good because sometimes he can't. Watching them gives him ideas on how to pleasure his wife, and it would make him hard, turn him on a lot, making him fuck his wife better than usual. Reclaiming her.
Another thing is that both of his children have lighter skin tones than both their parents. Both of them might have a bit of a fetish for white men, or at least watching men with skin lighter than himself fuck his wife. Maybe they both have a fetish for white people, and that fetish results in his wife fucking white men more often, or men that are lighter skin than both of them. As a result of that, when she got pregnant, the children came out whiter than the both of them, and they didn't care, and people don't tend to public question things like not looking like a parent.
The children don't seem to know, but maybe they do know, they don't seem to make that public. Maybe if they did know, they'd have a thought about being in a similar relationship. Rocky's potential future relationship, her husband is absent frequently, which could lead to her pursing a relationship in a similar vein, maybe having the same white man fetish that her mother has.
Either way, it's clear that those children aren't actually his, and he was no problem with it.