Gwen Stefani, 51, tasked her two eldest children with a very important role on the No Doubt frontwoman’s wedding day to Blake Shelton, 45. The couple’s wedding certificate was obtained by TMZ and shows that Gwen’s sons Kingston, 15, and Zuma, 12, both signed as witnesses before the July 3 Oklahoma ceremony. Gwen’s youngest son, Apollo, 7, did not sign on the paperwork, though he of course was present to witness his mom say “I do” to Blake.