The actor's cousin, jewellery designer Farah Khan Ali shared the news via Twitter, and congratulated the new parents.
"Woke up to wonderful news. My cousin Fardeen and his wife Natasha were blessed by a beautiful baby girl Diani Isabella Khan yesterday (Wednesday)," Farah posted on the microblogging site on Thursday.
"God bless my little niece with loads of health, wealth and happiness. Congratulations to the parents," she added.
This good news comes after a tragic miscarriage of twin babies that Natasha went through last year.
Natasha, who is the daughter of veteran actress Mumtaz, married Fardeen in December 2005. Fardeen, who has featured in films like Om Jai Jagadish, No Entry and Heyy Babyy, is the son of late actor Feroz Khan.