Ashlee Simpson thinks her mother-in-law, Diana Ross, is ''brilliant''.

The 33-year-old singer - who has son Bronx, nine, from her marriage to Pete Wentz and daughter Jagger, three, with husband Evan Ross - is always inspired by the Motown legend and admitted the 'You Can't Hurry Love' singer is a vital part of their family.

She said: ''I love [Diana]. She is a brilliant mother-in-law and a great grand-mommy. 'Omi' the kids call her.

''She is a great mother and has also had a great career. It's inspiring.

''When she is there, you can feel her energy, which takes you to new heights.''

Diana can be seen mentoring Evan and Ashlee in their new reality show, 'Ashlee+Evan' - which features them making an album together - and the couple are always happy to listen to her advice.

Evan said: ''My mom has always been really involved in all the stuff I do and she was supportive of me and Ashlee making an album. She always gives great advice.

''She tells us to trust our gut. She's also so great with melodies and storylines She loves the album and its message.''

Evan, 30, admitted his mother's success is a lot to live up to but he hopes he makes her proud.

He said: ''Growing up with a mother like that, you dream big!

''I think I'm making her proud and I try to keep doing the best I can.''

While the pair have enjoyed working on the show and the music featured within the series, they admitted it could be difficult to fit filming in around their family life.

Ashlee said: ''There were moments due to scheduling where we'd have to be like, 'Actually, as much as we want to work together to make music, one of us has to go home and see the kids.' ''