Ashlee Simpson says Diana Ross is "so hands on" as a grandmother.

The 40-year-old singer and reality star married the iconic musician's son Evan in 2014, and she has opened up about how the Chain Reaction hitmaker acts around her grandchildren.

Asked how she is as a grandmother, Ashlee told E! News: "The best one! So hands on, and you wouldn't think of it like that. She's just about family."

The loved up couple have kids Jagger Snow, eight, and Ziggy Blu, three, together, while the singer has son Bronx Mowgli, 15, from her previous marriage to Pete Wentz.

Ashlee recently announced plans for a Las Vegas show, and she admitted she could be raiding Diana's closet for outfits.

She quipped: "I would love to steal anything. Any time she's given me anything I'm like, 'Oh my God, this is the most beautiful piece!'

"Her archive is beyond insane, so anything she's willing to give me I'll put on for good luck'...

"We've seen in her Vegas so many times, she's always inspired me. She's a mom, she keeps it altogether, she's a grandma, she's Diana Ross!"

Meanwhile, Ashlee also opened up on what their family is like over the holidays.

She added: "They are [lit], the kids have so many cousins. We're all in one home, everyone's playing, the kids are all together. No one ever wants to leave."

And while she's happy and in love with her "best friend" Evan after over a decade of marriage, her bond with sister Jessica Simpson is still a key part of her life.

She said: "I think those things are just a part of what came with our lives. Together, we're always strong.

"We definitely know how to overcome those things, and not harp on them, and not look back, and move forward.

"We always have the best time together. Nobody knows you better than your sibling, you don't even have to say anything, you just get it."