Sir Mick Jagger appears to have named his newborn son Deveraux Octavian Basil Jagger.
A photograph of the baby, Sir Mick's eighth child, appeared on an Instagram account under the name of Elizabeth Jagger, one of the Rolling Stones rocker's other children.
The caption read: "My beautiful baby brother Deveraux Octavian Basil Jagger."
Basil was the first name of Sir Mick's late father, who died in 2006, although he was known to others as Joe.
Sir Mick became a father again at the age of 73 on December 8, with his partner Melanie Hamrick, 29.
Elizabeth, commonly referred to as Lizzy, is followed by more than 50,000 people on her social media account, although it is not verified.
Sir Mick, who is a great-grandfather, has six other children as well as Lizzy and his one week-old son - Karis, Jade, James, Georgia, Gabriel and Lucas - from previous relationships.
Their ages range from 17 to 46.
Sir Mick and Melanie began dating after the death of fashion designer L'Wren Scott in 2014, Sir Mick's partner of 13 years.
A representative for Sir Mick has been contacted.