I think during that time period it was normal for a man to have multiple wives (as seen in other boran lakorns/movies) and even if they don't have "official" 2nd, 3rd, etc wives who they marry legally, they still have relationships with the maids/servants. I think P'Pin had said that those were the servants' kids so the dad must've had relations with the servants, that's why the kids are living with the servants instead of in the big house. As seen in other lakorns, if they were kids with the official/legal other wives, they'd be living in their own little house and have their own servants? Just like how Louis had said to Malee, he's a guy, he picks up any "wild flower" on the side of the road whether it's pretty or not (which made me roll my eyes back so hard, like wtf Louis, but I had to keep in mind that it was his character not him)