Mandy Dawn Cornett and Brian Teefey with Selena Gomez (inset)
has something to be thankful for this holiday season – she's going to be a big sister.
The singer, 19, posted the baby news along with a photo of her mother, Mandy Dawn Cornett, and her stepfather, Brian Teefey, on her Instagram account
"Momma and Brian are finally letting me share the news," she wrote in the post. "My mommys carrying my baby brother or sister :) I'm the happiest girl in the world!"
This will be the first child for Cornett and Teefey, who married in 2006.