Granger and Amber are also parents to son Lincoln, 7, and daughter London, 9.
Granger Smith is a country music artist from Dallas, Texas and has been crossing over into mainstream country music for the past few years.
He later posted more photos in his story, including a pic of Amber holding and kissing baby Maverick and a shot of himself holding the baby with a tattoo of River's name visible on his forearm.
With such a small body, organs had to be measured physically, not just by X-ray.
When Anheuser-Busch chose Amber Smith as the spokesperson for its new Michelob Ultra Amber lite beer, it was on a mission.
The 41-year-old country singer and his wife announced on Thursday March 11 that they are expecting a baby boy, due in August.