Stewart is the son of Nils Allen Stewart, Sr., and Renee Stewart. He has three sisters: Trent "Fivel" (b. 1996), Maegan, and Sage. He was inducted into the Martial Arts Junior Hall of Fame in 2004. He is now on tour with his two sisters Maegan and Fivel, known as TSC (The Stewart Clan). He is a fan of professional wrestling and has pictures of himself with various WWE stars on his official Myspace page. He also attended Summerslam 2009 and was featured heavily in video packages on WWE programming following the event. In October 2009, Booboo and his family attended TNA Wrestling's Bound for Glory PPV which took place at the Bren Events Center in Irvine, CA. Booboo's real name is Nils Allen Stewart Jr., but he was nicknamed Booboo as a child because he used to suck two fingers and his mom said that he had a booboo face.
Stewart claims that he is of Chinese, Japanese, Korean, Russian, Scottish and Blackfoot (Native American) ancestry.
Stewart is a former member of Disney's T-Squad and now tours with two of his sisters—Fivel and Maegan.
In 2011, he received the 2011 Rising Star Award from the Temecula Film and Music Festival.
In 2012, Stewart's ad for PETA was released. Stewart is the third actor from the Twilight Saga to have an ad for PETA.
In 2014, he co-starred with Daniel Cudmore in the Marvel movie, X-Men: Days of Future Past as Warpath.
|2004||Yard Sale||Little Boy|
|2006||18 Fingers Of Death!||Young Buford|
|The Conrad Boys||Ben Conrad|
|666: The Child||Donald|
|2007||The Last Sentinel||Young Tallis|
|Uncle P||Bike Kid.|
|2008||The Fifth Commandment||Young Chance|
|How I Survived the Zombie Apocalypse||Son||Short film|
|2010||Dark Games||Jake Wincott|
|The Twilight Saga: Eclipse||Seth Clearwater|
|2011||Jake Stevens: The Last Protector||Jake Stevens|
|The Twilight Saga: Breaking Dawn - Part 1||Seth Clearwater|
|2012||The Twilight Saga: Breaking Dawn - Part 2||Seth Clearwater|
|White Frog||Nick Young|
|Guardians of Luna||Jake Segerstrom||Voice|
|2014||X-Men: Days of Future Past||James Proudstar/Warpath||Co-starring Daniel Cudmore|
|2015||Descendants||Jay||Disney Channel Original Movie|
|Film made for television|
|2004||Skelton Man||Child Warrior||Sci Fi Pictures orginal film|
|Television guest appearances|
|2004||Big Time||Martial artist||Unknown episodes|
|2004–2006||Dante's Cove||Stephen||5 episodes, 1 episode credit only
Unaired pilot as Boo Boo Torra
|Power Ranger||Episode: " Man With No Name"|
Everybody Hates Chris
|Blue Dolphin Kids||Himself / Host||11 episodes, 3 episodes as Actor|
|2010||CSI: Miami||Kenny Turner||Episode: "Die by the Sword"|
|2011||Good Luck Charlie||Kai||2 episodes ("Sun Show Part 1", "Sun Show Part 2")|
|R.L. She's The Hauning Hour||Kai||1 episode ("Pool Shark")|
|2012||Kickin' It||Carson||1 episode ("New Jack City")|
|2015||Descendants: Wicked World||Jay||Voice; 2 episodes|
|2008||Kung Fu Fighting||Cee-Lo Green and Jack Black|
- Stewart's favorite book in the Twilight Saga is Eclipse.
- At the 2011 Seattle Twilight Convention, when asked what team was he on, he replied, "Well... Rob, you know..."