The Swiss tennis star announced through Twitter on December 24th that his wife Mirka was pregnant.
Mirka is now expecting in July and sources close to the family say the Federers can expect twins again, 20 Minuten reported.
Neither Federer nor his wife have commented on the report.
The couple’s identical twin daughters Myla and Charlène were born in 2009.
Twins are a going concern in Federer’s family.
The eighth-ranked tennis player’s older sister Diana is also mother to a pair.
As 20 Minuten points out, twins are not unusual among well-known sports figures.
The likes of Lance Armstrong, Pele, Michael Jordan and Peyton Manning are all fathers to twins.
But Federer, holder of 17 Grand Slam tennis titles, could set another first if the prediction for July comes to pass.