If this isn't the most Mariah Carey move of all time we don't know what is ... 'cause teaching her twins backup vocals is pretty legendary.
Mariah put Moroccan and Monroe to work Wednesday night, teaching them the backup vocals to her 1994 classic "All I Want For Christmas Is You." You can tell the kids have listened to this song once or twice ... they jump on cue when the song starts.
Roc and Roe -- as Mariah's dubbed them -- are definitely into this. You can see Moroccan crack his fingers and dab before putting in some work. Mariah kicks things off before the kiddos jump in with their I's and O's.
Mariah says the kids have been practicing the vocals ... and bravo, 'cause they nailed it.
Moral of the story ... never too early to put your kids to work. JK ... it's about family QT or whatever.