KouAidou
二番目の翻訳者
I suppose it's possible that Saeko inherited her style of dumping boyfriends from her daddy, and Ryubee might have had kids with multiple wives? But, yeah, the flashback was going for more of a happy families look ...
Well, if Philip were the product of an affair, the other girls might not know about it. The Sonozakis seem like the kind of upper-class family that Would Not Acknowledge such an indiscretion.
Personally though I don't really see a need to have Saeko/Wakana/Philip have different moms. It would be one thing if there was a Mrs. Sonozaki walking around, but since there's no mom in the picture at all at the moment, having a dual-revelation seems like it would be sort of unwieldy. Unless Philip is totally adopted, he and Wakana would still be half-siblings and their relationship is still creepy.
Thinking about it, I could almost buy Philip as having a different father than the others, if anything. If Mama Sonozaki had been sleeping around and Ryubei were bearing the indignity of raising the illegitimate son as his own, it would pretty well explain why he was willing to use Philip entirely as a dehumanized tool for world domination. And why Mama would be really desperate to save Philip from their clutches.