Sarah Palin is about to be a grandmother again.

Bristol Palin announced on blog Thursday that she is pregnant with her second child, writing "honestly I've been trying to keep my chin up on this one."

Palin, 24, was set to be married to U.S. Marine and Medal of Honor recipient Dakota Meyer on May 23, but her mother announced a week before the wedding that it had been called off. Palin did not indicate who the father of her new baby is.

"I know this is has been, and will be, a huge disappointment to my family, to my close friends, and to many of you," Palin wrote.

Palin is mother to Tripp, 6. She famously announced her pregnancy just days after her mother was selected as John McCain's running mate in 2008.

Sarah Palin, the former governor of Alaska, also has a granddaughter, Kyla, 3, the daughter of Palin's son Track and his ex-wife. Track and Bristol Palin, along with younger sister Willow, made headlines last year when they were involved in a brawl in Alaska.