The Chelsea midfielder, who is himself father to one-year-old Lia with his partner Daniella Semaan, gained a new baby sister when his 45-year-old mother Nuria Soler gave birth this week.
Cesc's other sister Carlota Fàbregas released a photo of the family's new addition on Wednesday.
Cesc, 27, and his newborn sister Claudia
"Hello, baby Claudia," she wrote next to one photo, while another was captioned: "My mother is a champion".
Cesc has yet to mention little Claudia on his multiple social media accounts,
The Spanish footballer has been dating Daniella
The Arenys de Mar-born sportsman regularly posts pictures of his daughter Lia and 38-year-old Daniella.
Rumours recently circulated that wedding bells are on the horizon for Cesc and Daniella after the brunette beauty was spotted wearing a large diamond on her ring finger.
While Cesc has not been married before, his Lebanon-born girlfriend was previously wed to property tycoon Elie Taktouk, with whom she has a son and a daughter.