The Rolling Stones have been a rock 'n' roll band for so long that in 1980, just before his death, John Lennon famously quipped that critics were "congratulating the Stones on being together 112 years. Whoopee!"
The group, which has rocked since 1962, has always been powered by the classic singer-guitarist duo of Mick Jagger and Keith Richards. Together, they're magnetic. Richards' guitar lines wrap seductively around Jagger's vocals seamlessly.
But theirs is a contentious relationship marked over the years by insults and the occasional breakup rumor. Richards, in particular, has aggressively tossed barbs at Jagger.
The most recent came in a Wall Street Journal profile in which Richards criticised Jagger's decision to father his eighth child at the age of 73: "It's time for the snip - you can't be a father at that age. Those poor kids!"
Other news outlets seized upon the quote, which quickly went viral on social media, prompting Richards to offer a rare public apology.
"I deeply regret the comments I made about Mick in the WSJ which were completely out of line," Richards tweeted. "I have of course apologised to him in person."
Tension between the bandmates first publicly bubbled over in 1985, after Jagger released his first solo album and then refused to go on tour in support of the 1986 Rolling Stones record "Dirty Work."
At the time, Jagger was also reportedly considering going on a solo tour, which might have been the end of the Rolling Stones. Richards has referred to the following few years as "World War III."
"I really believed Mick wouldn't dare tour without the Stones," Richards told Rolling Stone magazine. "It was too hard a slap in the face to deliver us. It was a death sentence."
Jagger was unapologetic.
Talking publicly about the feud "only goes to fuel more troubles, and Keith gets real upset every time I say anything that's even nice or understanding," Jagger said. He added: "I think that one ought to be allowed to have one's artistic side apart from just being in the Rolling Stones. I love the Rolling Stones - I think it's wonderful, I think it's done a lot of wonderful things for music. But, you know, it cannot be, at my age and after spending all these years, the only thing in my life."
Jagger released a second solo record in 1987. Soon after, Richards released his own solo album.
Meanwhile, the Rolling Stones were dormant - and many thought finished. As Colin Larkin wrote in the "Encyclopedia of Popular Music," "When Richards himself released the first solo work of his career in 1988, the Rolling Stones' obituary had virtually been written."
But the two appeared to reach what Rolling Stone magazine called "an uneasy truce" in 1989, when the band released "Steel Wheels" and began touring again.
For a while, the bandmates seemed blissfully reunited, writing some of their best-reviewed recent albums, including 1994's "Voodoo Lounge," 1995's live album "Stripped" and 2005's "A Bigger Bang."
Then came the 2010 release of Richards's memoir, "Life," which overflowed with brutal insults aimed at Jagger, including swipes at his anatomy.
"It was the beginning of the '80s when Mick started to become unbearable," Richards wrote, adding that as an insult the band would call him "Brenda, or Her Majesty, or just Madam." That's also when Jagger had lost his skill and had "taken up singing lessons," Richards said.
He also said Jagger had a "swollen head" and an "inflated ego."
"Mick got very big ideas," he wrote. "All lead singers do. It's a known affliction called LVS, lead vocalist syndrome."
Toward the end of the autobiography, Richards admitted that he once enjoyed Jagger's friendship.
"I used to love to hang with Mick, but I haven't gone to his dressing room in, I don't think, twenty years," he wrote. "Sometimes I miss my friend. Where the hell did he go?"
A couple years after the book's publication, Richards offered a half-apology.
"As far as the book goes, it was my story and it was very raw, as I meant it to be, but I know that some parts of it and some of the publicity really offended Mick and I regret that," he told Rolling Stone magazine.
Jagger spoke to writer Rich Cohen for a 2016 book on the band, "The Sun & The Moon & The Rolling Stones." Cohen wrote that Jagger was angry and hurt by Richards' book and asked him to remove certain passages. Richards refused.
Cohen, paraphrasing Jagger, wrote: "Imagine that everything Keith says is true. Now imagine those things being said by a business partner. ... Now imagine that partner is drug addicted. Sometimes, you have a big meeting and he doesn't show. ... Or maybe he gets busted on the eve of a world tour. What, in such a case, would you make of his complaints?"
Whatever public face the band puts on these days, Richards still tosses jabs at Jagger from time to time - particularly about the singer's five solo records. As recently as November 2015, Richards told GQ that the singer's solo work "had something to do with ego. He really had nothing to say."
That time, Richards didn't apologize. Why would he? Richards said the fights are good for the band, which just announced 11 summer shows in Europe.
"Mick and I live off of this fire between us," he told the Wall Street Journal.