https://www.dlsite.com/books/work/=/product_id/BJ176863.html

Dlsite Intro, translated:

I'm Yasuto. Makie-san and Sakura-san, who are sleeping next to me, are both my wives. They are sisters with a somewhat unfortunate past, but from now on, I'll love them well and make them both happy!

I have no idea if the woman with black hair & glasses is the Sisters' Mom, or the Boy's Mom

Base +7, McKatarn -6

Page 46
She gave birth to him at 16 years old.

Base +20