M6 and J7 are twin brothers who live in alaska they apperead in several episodes(such as Ski trip pt 2 and 3 who they helped Kelvin(K2) to he don't freeze in the ice and sheltering him in the shack of them,and also getting invited to a reunion by David(D1) in Yo-kai Wacht episode 9) and we actuly know the names of them they are Mike and Jeremy(they are inspired from the nightguards from FNaF 1 and 2 Mike Schmidt and Jeremy Fitzgerald)

M6 real name is Mike(Michael)

J7 real name is Jeremy(Jerry)