“Mum, Ava and Kitty doing well! Dad overjoyed,” he wrote.
“Thanks to all at the hospital!”
Earlier in the day Kemp shared a selfie with gynaecologist Lawrence Impey, showing them both in scrubs.
“Big thanks to Lawrence Impey and his team. Very happy Dad again!
Kemp and O’Brien, also have a son together who was born in April 2015. He also has an older son with his former partner Nicola Coleman.