Roger Federer's family will be growing pretty soon.

The tennis star announced on Twitter that he and his wife, Mirka Federer, are expecting another child next year. Roger wrote Wednesday, ''Mirka and I are very happy to share the news'' that the couple's daughters ''will be big sisters in 2014!'' Identical twins Charlene and Myla were born on July, 23, 2009.

The athlete's agent, Tony Godsick, confirmed to The Associated Press the tweet is true. Roger did not reveal how many months Mirka is already pregnant and did not state the baby's gender.

Roger and Mirka first met at the 2000 Summer Olympics and wed in April 2009. Mirka officially retired from playing tennis in 2002 because of her recurring foot injury, International Business Times reported. She has supported him throughout his career and has been spotted at his games on numerous occasions.

The 32-year-old Federer has won a record 17 Grand Slam singles titles and spent more weeks at No. 1 than anyone else in the history of the ATP rankings. He heads next week to the Brisbane International Tournament, which is from Dec. 29, 2013, to Jan. 5, 2014 on outdoor hard courts at the Queensland Tennis Centre in Tennyson. This will be the player's first-ever participation in the tournament.

Federer has been training hard in Dubai for the upcoming Australian Open Championships and he holds No. 6 place in the latest ATP Rankings, according to Live Tennis Guide.