The couple announced the news on Instagram by sharing a picture of themselves sitting in their bedroom.
"This is how I told my son babies are made. #numbertwo #nosefrida @fridababy #teetsreincarnated," Mollen, 37, captioned the shot of she and Biggs, 38, using the Fridababy NoseFrida, a device that allows parents to suck and catch the snot out of their newborns' noses.
The pair tied the knot in 2008 and welcomed their first child, a son, in February 2014.