Gwen Stefani shared photos on Instagram of her helping her boyfriend, Blake Shelton, celebrate his 41st birthday on Sunday. "The Voice" coaches have been dating for about two years. "I get to kiss on the birthday boy @blakeshelton #happybirthdaycowboy," Stefani captioned a closeup selfie of her kissing Shelton under the visor of his baseball cap. Stefani also posted the message, "Celebrating the birth of my #bestie #favorite @blakeshelton," along with a short video of Shelton with a gift balanced on his head and tied to balloons. "Birthday armadillo @blakeshelton gx #bdayboy #cake," read the message that went with an image of Shelton's birthday treat -- an armadillo-shaped cake.