The oldest child of Barrett Williams and New Kids on the Block singer Joe McIntyre, he was born and raised in Los Angeles, California.
His parents married in August of 2003.
After parting ways with his fellow New Kids on the Block members, Griffin's father released several solo albums, including Stay the Same and Meet Joe Mac.
His younger brother, Rhys, was born in late 2009, and his little sister, Kira, made her debut in the spring of 2011.
His father and Jonathan Knight both rose to fame as members of the boy band New Kids on the Block.