They frolicked in front of the camera for their 1985 remake of Dancing in the Street and have for many years moved in the same circles of rock royalty.
Now, adding fuel to rumours that have for years abounded, a new book claims that Mick Jagger, 68, and David Bowie, 65, arguably the most dynamic and influential rock stars of their generation, were once lovers.
The incendiary claims, neatly timed with the 50th anniversary of the Rolling Stones' first gig, have been made by Christopher Andersen, author of Mick: The Wild Life and Mad Genius of Jagger.
Speaking with friends and family of the seemingly ageless rockers, at least four of the showmen's glamourous set have recalled stories of the men's antics. The two had a deep respect for each other, Mike (as Bowie knew Mick) admiring Bowie's creativity, and Bowie admiring Jagger's "financial genius" as the frontman of the Rolling Stones, writes Andersen.
The men, he says, were "fascinated with each other."
"When Bowie and his companion Scott were invited to a Stones concert a few months later, Mick not only paid for the couple’s hotel room but sent along roses and champagne with a note signed "Love, Mick.""
This was 1973, after all, and, as singer Chuckie Starr told Andersen: "It was the glitter era, and everybody wanted to be part of the bisexual revolution".
Having had a hit that year with Starman, Bowie - in the public guise of Ziggy Stardust – experimented with androgyny, embraced glam-rock and was apparently open about his (and wife Angie's) bisexual extra-marital love-life. Jagger had famously worn glitter on his 1972 US tour, echoing Bowie's eccentric style.
"Bowie and Jagger were soon spotted everywhere together without their wives: sitting ringside at the Muhammad Ali-Ken Norton bout, hanging out at the London disco Tramp, yelling and stomping their approval at a Diana Ross concert, or just cuddling up together on a hotel room couch," Andersen alleges.
"Neither superstar complained when one enterprising photographer snapped the two men in a moment of repose, Bowie tenderly cradling Mick’s head in his lap.
"Bowie also took Mick to gay films." When they met, Jagger had two children by Martha Hunt and Bianca Jagger - and went on to father five more children with Jerry Hall and Luciana Gimenez.
The men frequently engaged in threesomes, but had a deeper emotional bond too, said Ava Cherry, a backing singer. She recalls some of their steamier moments together: "Even though I was in bed with them many times, I ended up just watching them have sex."
Bebe Buell, a Playboy model who had daughter Liv Tyler with Aerosmith frontman Steven Tyler, recalls being pursued by Jagger, and went on to sleep with both men. She too claims that bedroom activity was wild and far from monogamous.
"I used to get some pretty strange phone calls from Mick and David at three in the morning," she told Andersen, "inviting me to join them in bed with four gorgeous black women ... or four gorgeous black men."
But it was the moment that Bowie's wife Angie caught the two men in bed together that seems to cement the rumours.
The blonde, with whom the singer had a son in 1970, Zowie Bowie (now Duncan Jones), says she one day found the men curled up in bed together, asleep.
She said she "felt absolutely dead certain that they’d been [having sex]. It was so obvious, in fact, that I never even considered the possibility that they hadn’t been".
In another revelatory tale, the controversial book also claims that Jagger became obsessed with Angelina Jolie after meeting her on a music video set in 1997. The singer is said to have "bombarded her with calls" and was "virtually sobbing" over the actess who was at the time married to Jonny Lee Miller.
Rewind to the 70s and Andersen writes that Angie worried about the damage that Jagger may do to Bowie's career - particularly amongst his younger fan base, though Stones band mate Keith Richards was perplexed by the relationship.
"The fact is," Richards states, "Mick could deliver ten times more than Bowie in just a T-shirt and a pair of jeans. Why would you want to be anything else if you’re Mick Jagger?"
Many a Ziggy Stardust fan may disagree - and almost 40 years since the two men met, it appears that the relationship did little damage to either man's phenomenal international success.