On Friday (31 July), reports suggested that the couple had welcomed a child together and now singer Evan has told the world the good news is true.
In a post on Instagram, 26-year-old Evan said: "We are overjoyed about the birth of our precious baby girl Jagger Snow Ross."
Could the name be a tribute to Rolling Stones front man Mick Jagger?
Fans were quick to comment on the unusual name, with one saying: "Congratulations Ross and Ashlee, your daughter's name is beautiful."
Another gushed: "OMG, such a beautiful name."
Not everyone seemed to like the name, however, with one lamenting: "Jagger? Poor baby she's going to be teased for life. Lol. Congrats Evan and Ashlee!!"
In a recent interview, Hunger Games star Evan promised the name would be "unique", adding: "You guys will figure out the story behind it once we tell the name."
Jagger is Ashlee and Evan's first child together... Ashlee has a son Bronx Mowgli, six, from her first marriage to Fall Out Boy star Pete Wentz (who she divorced in 2011).
Singer/actress Ashlee, 30, and Evan - son of legendary disco diva Diana Ross - confirmed they were expecting a daughter in February after months of speculation.
Their baby joy comes almost one year after the couple tied the knot in Connecticut at Diana's estate in August 2014.
Until now they had kept their nuptials private, but Evan shared a series of his and Ashlee's wedding photos to Instagram earlier this week.
What do you think of the name Jagger Snow? Tell us your opinion in the comment box below!
For exclusive competitions and amazing prizes visit Reveal's Facebook page NOW!