Bandori is the shorter version of saying BanG Dream... BanG Dream in Japanese is pronounced bangu doriimu, so fans took ban + dori and made it a sort of abbreviation. Hope this helped!
This is so cute lol!
EDIT: Who cares if they had babies from the "thing"? If they would rather do that than go through the expensive and lengthy process of adoption or IVF (in vitro fertilization), both of which not guaranteed to work, then let them do that. Sincerely, a lesbo