Kelly hasn't shared details about when the baby is due.
But the star has been candid about the couple's attempts to start a family, revealing last month getting pregnant was at the top of her Christmas list.
"Everybody keeps saying, 'What do you want for Christmas?' And I'm like, 'I want to be pregnant.' I want babies, yep! I do," she told radio host Sean Valentine.
She spoke openly during an interview for radio show Valentine In The Morning while promoting her new Christmas album Wrapped in Red.
The Since U Been Gone hitmaker said it was her role as a stepmother to Brandon's children that convinced her she wanted a family.
"I honestly never ever used to want to want kids because I'm kind of selfish with my career, but going to soccer games with Seth and doing homework with Savannah - I just really love it y'all.
"It's so cool. It sounds so cheesy but it's such a bigger point to life," she said.
- Cover Media
