Kim Zolciak's Husband Kroy Biermann -- I Wanna Adopt Kim's Girls!

Kim Zolciak's NFL star husband Kroy Biermann wants to pack on about 200 lbs ... OF LOVE ... as he's decided to legally adopt the "Real Housewives" star's two girls from her previous marriage.

Sources tell TMZ ... Kroy is set to file paperwork in Georgia court (it's a process) to become the legal father of 15-year-old Brielle and 11-year-old Ariana. FYI -- the girls' biological father has been out of the picture for awhile.

According to our sources, Kroy -- who plays for the Atlanta Falcons -- considers the girls his own and wants to make it official. We're told Kim already gave her blessing and the girls are 100% on board.

Kroy is headed to court next month, where a judge will have to sign off on the adoption.