Talk:Saiki Kumagoro/@comment-203.215.117.97-20161009011854/@comment-25234961-20161009040001

"Kumagoro is Kurumi's father. Apparently both of Saiki's parents had Saiki as their family name, even before they got married (Saiki's dad thinks it was fate, Kusuo just thinks it was coincidence lol)"

This is the answer of eyfey the translator of SKNS manga.

As for when it was mentioned...

"'it's in ch92 when they go to visit the grandparents for the first time~ Saiki mentions it in a couple panels"