The 25-year-old made the announcement on social media.
Stefanos Tsitsipas sees NextGen stars challenging for Slams in 2020.
The couple announced the birth of Keira, who was born on September 27.
Marin Cilic's family will be expanding in 2020.
Former world No. 3 made history winning 1972 French Open crown.
World No. 2 aims for return at Paris Masters.
Former No. 1 set for Grand Slam singles return at Australian Open in January.