Jeffy is generally recognized for being a foul-mouthed, ill-behaved, dumb, perverted young teenager with an unusual personality and a strange choice of clothing. Jeffy is the adoptive boy of Mario and his spouse, Rosalina.
Jeffy was born in a Port-A-Potty in Paris, France in 2004. He never ever went to any school because of his mom lacking any care for him.
After his parents very likely got divorced, Jeffy was taken by his mother and smuggled into the USA as an illegal migrant. She left Jeffy at Mario and Bowser’s apartment given that his mother was fed up of his stupidity. He now lives with Mario and his family in the All-new Residence.
Feebee, his young sister, was likely killed in a bicycle crash as their mom took her safety helmet as an ashtray, obliging Jeffy to wear it continually.
Because his dad is the late wealthy painter Jacques Pierre Francois, Jeffy is of French descent and extremely proficient at painting. His mother, Nancy Francois, turned out to be an offensive mum and a lady of pleasure, who engendered Jeffy in a porta-potty. Mario adopted Jeffy soon after his abusive mother got caught for child abuse, prostitution, and several other matters.
Mario does this in the hope that when Jeffy turns 18, he grants Mario a portion of his bond money inherited from his father.