Do i file a jointly w wife as of 3/1/2020 (K1 FIANCE VISA) her, my 2 yr old son flew in dec 12th 2020 , me disability rep payee for him, her dependant or no? how?

she has a ss# just got it last week he has his he's duel. whats the best way to approach this ,filed last year as a single for the k1 but this yr is differant i need to get them on my taxes