The 55-year-old singer has been romancing 26-year-old dancer Timon Steffens and is delighted he gets on so well with 13-year-old Rocco, particularly as the teenager doesn't get to spend a lot of time with his father Guy Ritchie.
Madonna and son Rocco. Pic: Bang
A source said: "I'm sure Madonna loves that Timor has taken Rocco under his wing. He's not a father figure, more like a big brother, which Madonna feels is important - especially as Guy can't always be around.
Timon Steffens
"Timor's been giving Rocco dance lessons and taking him on shopping trips and will undoubtedly be helping him navigate all those tricky teen issues he doesn't want to talk to his mum about."
Madonna - who also has daughters Lourdes, 17, and Mercy, eight, and another son David, also eight - and Timor were first romantically linked on a skiing trip to Switzerland at the beginning of the year, but after being seen out together numerous times recently, friends say the relationship is getting more serious.
Pic: Bang
The source told Britain's Grazia magazine: "Until recently, they were keeping things casual, but things are gradually getting more serious."