Sullivan was born on July 12, 1991, in Worcester, Massachusetts, the only child of his mother, Ann, born in Sweden and naturalized as a US citizen in 2007, and Fred Sullivan, of Irish descent,[1] who owns a Mexican eatery called The Alamo.
Beginning in 2009, he attended the University of Southern California in Los Angeles.
In 2005, along with Malcolm co-star Jane Kaczmarek, he wrote the afterword to the children's book Together, which is about farming and was inspired by the nonprofit organization Heifer International.
Sullivan's last acting credit was an appearance in the 2010 film Twelve when he was 18 years old.
He has since kept a low profile, and was absent from several Malcolm in the Middle cast reunions.