That didn't make any sense to me. If they got married and had kids while they were in college how could the mother not know that they weren't related (unless she lied to her daughter about that, which doesn't seem likely) And weren't the two dads friends (base on the photo). Most of the time couple becomes friends which makes me believe that in all likelihood the mothers were friends or at least know each others. Also base on what the professor said, it is safe to assume that his parents died in college. All of those factors point to the mother knowing and even in the less likelihood that she didn't know- what wife doesn't ask her husband who the child is that she is raising (she did raise him for his primary years-if i remember correctly). And why wouldn't the husband tell her the truth- the lie makes him an asshole and could damage his relationship. To me it just seems like the mangaka is trying to end series with everyone coming out smelling like roses.
*shrugs* that's what the latest chapter says. The mother didn't know. And more current revelations tend to be the most accurate. Since it's the most recent thing the author wrote.
The manga is just riddled with plot holes. I mean, it's a shoujo manga with deus ex machine elements in it. There's going to be a lot of sloppily done plot lines with illogical reasonings. Especially when they're rushing the end.
Idk..I think she is still pretty awful for pressuring her daughter to marry a man she barely knows who is way older than her. In general she acts over the top controlling towards her. Like it's shoujo so it won't go that far but if it wasn't I could see their situation ending up like one of those dark psychological thrillers. I actually think she is abusive.
The dad said that the mom didn't know the two weren't related. She probably thought that yuzuru and ai were half siblings and yuzuru was from an earlier marriage. Which would still be a taboo relationship.