Hidan will be infuriated because I really don’t see him as the type who would ever be excited about having a baby. It’s just a nuisance. Which is why he’d take precaution when he had sex. Last thing he’d want is a baby. So to find out that his s/o is pregnant will just throw him for a loop. It’s not likely he’d step up to be a father, that’s just now Hidan

Kakuzu is equally displeased by the thought of children, even more so having children. He’s more likely to put up with it at first, but will inevitably become distant once he realizes he really just can’t handle it and that he has no interest in being a father

Suigestsu will be the one who at least tries. He’ll probably be a little frustrated that they got pregnant in the first place, especially if he was careful about it. Suigetsu has weak pull out game so if it’s his fault they were pregnant, he’ll be even more frustrated. He won’t be excited about it, but he won’t really reprimand his s/o because he doesn’t want to upset them. And if he really likes them, he’s more likely to go the extra mile and try to be a decent dad for the most part. He’s annoyed by kids, but he might make an exception for his child