People reports that the Sherlock Holmes star and his wife are proud parents to a new daughter, although the exact date and time of her birth have not been released.
Robert first announced that the couple were expecting another baby back in July, in a terse but informative tweet which has proven accurate:
Yo. Susan. Me. Baby. Girl. November. Scorpio?
- Robert Downey Jr (@RobertDowneyJr) July 9, 2014
Robert, 49, and film producer Susan, 40, are already mum and dad to two-year-old Exton, and Robert also has a 21-year-old son, Indio, from his previous marriage to Deborah Falconer.
The couple met in 2003, when Robert starred in infamously-panned Halle Berry horror Gothika, on which Susan worked as a producer. They wed in 2005, and Susan gave birth to their first child, Exton Elias, on 7 February, 2012.
Once the poster boy for troubled movie stars, Robert credits their relationship for helping him beat his battles with alcohol and drug addiction, which culminated in a year-long jail sentence in 1999.
The Iron Man actor has been in the news recently for his vocal tributes to his wife of nine years, calling her his 'hero' on Twitter and joking that 'every mother-to-be is a Navy Seal and a saint' in another tweet to his nearly three million followers.
In his acceptance speech at the BAFTA Los Angeles Britannia awards last week, Robert singled out Susan once more, wondering aloud: "How is she still so darn pretty and functional and mood-stable?" despite being 'literally about to pop'.
Neither Robert nor Susan have commented publicly on the baby news as of today (5 November).