Diana Ross watched Ashlee Simpson Ross give birth.

Evan Ross has revealed his legendary singer mum was an uninvited guest into the delivery room to see his 33-year-old wife in labour with their child, two-year-old daughter Jagger, and joked the nurses didn't feel as though they could say anything to his mother because of her fame.

When asked about the most memorable moment from the youngster's birth, he said: ''Probably our parents coming in before it was time to come.

''I was like, 'What are y'all doing?'

''While [Ashlee] was having the baby, we said we were going to do it just us, but then we saw both our parents behind the curtain watching.

''Also, those nurses can't stop my mom. Like, Diana Ross just walks in.''

Ashlee - who also has nine-year-old son Bronx from her former marriage to Fall Out Boy bassist Pete Wentz - is saving a collection of vintage Chanel dresses for her daughter to wear when she is older, and admitted the little one is already opinionated about what she puts on.

The 'Outta My Head' hitmaker said: ''I love dressing Jagger. It's so much fun for me.

''If she doesn't like something, she'll check it out in the mirror and tell me.''

Evan added to PEOPLE: ''She's very focused on dressing Jagger.''

Ashlee recently revealed Jagger has already set her sights on following in her famous grandmother's footsteps by becoming a singer.

She said: ''She's a little star already though. It's crazy. She's a star.

''She's into her Ami [Diana Ross]. She wants the sparkles and the microphone.''

Speaking about whether Jagger could pursue a music career when she's older, Evan previously said: ''100 percent. 1,000 percent. I don't know if we have a choice in the matter.''