Responses
i think the mother of tetsuo was only related to the novel and they only mention her to give an idea
http://www.mangago.me/read-manga/okane_ga_nai/mf/v10/c045.1/6/
and as u see from here i can tell that the father of kanou had an illegal sex with one of his lovers and then took the child and maybe broke up after or she was died this is why he said he did say he has no mom also there is an extra about ayase and his grandma who was so conserative in volume 3 i guess and they did not translate it to english （￣へ￣）
btw, does anyone ever see the characters mom mentioned in the manga at all? IIRC, all we see is the dads. I'm kinda curious to see the moms, I bet they have strong personalities too especially Kanou's mom