- Main article: Washington family
Marvin's parents are Ed and Elaine. He has two siblings, Tamika, and a so far unheard older brother, Antoine, who is away at college. Their cousin Xavier lived with them because his mother was having some hard times. Also living with his family now is Kelly, a girl they've taken in as a foster child.
Marvin takes piano lessons, but the keyboard "fails to inspire him" and his true love is playing the drums. He even once started a band, Los Perros Frescos (Spanish for "The Cool Dogs") in The Coolest Dog with Tamika, Wooton, and his best friend Trent DeWhite, which is only seen once, although Tamika mentions in Odyssey Sings! that she's been "singing for [her] brother's garage band". Marvin also claims to be the "Fundraising Master"--he could sell a light bulb to a bat. In A Capsule Comes to Town he works briefly with Harlow Doyle.
- His birthday is in December. (#558: “A Glass Darkly”)
See Washington quotes.