Madonna is reportedly getting more serious with her toy boy lover Timor Steffens.

The queen of pop has been linked to dancer Timor since New Year's Eve. Sources close to the couple say the relationship hadn't been too serious, but things have now started to step up a gear.

An insider revealed the 4 Minutes singer is particularly pleased with how well her beau gets on with son Rocco, who she has with ex-husband Guy Ritchie.

"Until recently, they were keeping things casual. But things are gradually getting more serious, and I'm sure Madonna loves that Timor has taken Rocco under his wing," a source divulged to British magazine Grazia. "He's not a father figure, more a big brother, which Madonna feels is important - especially as Guy can't always be around."

Rocco, 13, and Timor were snapped together on a winter break in Switzerland, the same time it's thought the relationship started with Madonna.

At 26, Timor is fairly close to Rocco in age and the pair have reportedly been bonding over mutual interests.

"Timor's been giving Rocco dance lessons and taking him on shopping trips, and undoubtedly will be helping him to navigate all those tricky teen issues he doesn't want to tell his mom about," the source added.

Since Madonna, 55, split from movie director Guy, 45, in 2008, she's been linked to a string of younger men. She enjoyed a three-year romance with dancer Brahim Zaibat, but they split last year.

Madonna's never been shy about her preference for younger men, but has previously admitted it wasn't a conscious decision to go for toy boys.

"I didn't, like, write down, 'I'm now going to have a relationship with a younger man.' That's just what happened," she laughed.