They didn’t meet until they were 14, 15 and 16. The OP was avoiding teenage years.
Also avoiding siblings, for some of you others who missed it 
Guitarist Kirk Hammett of Metallica and bassist Les Claypool of Primus grew up together in Richmond, California, and were in the same graduating class at De Anza High School.
Total change of pace- Neil Diamond and Barbra Streisand were classmates at Erasmus High School in Brooklyn.
David Bowie is a few years older than Peter Frampton, but they grew up very close together. In fact, Frampton’s Dad was Bowie’s favorite teacher at Bromley Technical High School.
I didn’t know that thanks.
I specifically said before high school since they usually draw from a larger area. And being in a band doesn’t necessarily mean you are a great technical musician. Even in successful bands.
I knew about the lessons but I don’t know how young they were.
Doesn’t count. Said it in the OP. Not random chance. That’s cheating.
Still love them. Paul Simon is an amazing song writer. There voices are perfect together. But Garfunkel is primarily a singer and no one is going to see Paul Simon for his competent guitar playing.
I didn’t know that either. I would certainly rank them as great musicians.
At what age is the question. As you get older you generally have a much larger pool of classmates to pull from. It is more likely that two or more great musicians will find each other in high school or college. In the case of Lee and Lifeson, they were friends before they were even musicians let alone great ones.
I am certain it is rare. I’m just interested to see how often it has happened with known musicians.
If Wikipedia can be trusted, George and Paul met on the schoolbus when they were 11 and 12, so they might qualify for the OP. I think by the time they were all in the Quarrymen, though, they were teenagers.
But he didn’t bring her flowers.
Many of the guys who revolutionized jazz in the 40s and 60s were from NYC.
John Myung, John Petrucci and Kevin Moore of Dream Theater were also childhood friends.
Ian Gillan and Pete Townshend were classmates at Acton Grammar, which raises the intriguing thought of what a Gillan-voiced Who would have sounded like.
Claypool auditioned for Metallica after Cliff Burton’s death. He didn’t make the cut.
Most, if not all, of the members of Fishbone, who are an incredibly talented punk/funk act, went to the same high school and met in that school’s music program. Their best-known song is “Party At Ground Zero”.
I have a small company shooting concerts.
My main clients are various locations of the School of Rock, an after-school program for kids age 8 through 18. Three times a year, each location puts on a series of concerts. The kids learn the show and practice for 12 weeks, then do a pair of public performances. The very best kids in each location form a band, and gig around town to get experience and promote the School. The very best of those kids can audition to become an “All-Star” and tour and play festivals like Lollapalooza and Gathering of the Vibes.
So, with 150 locations in the US and seven other countries, I think that, in the future, the *default *will be that bend members have been playing together for years before they officially start a band.
I like picture #2. Large extended family looking happy and relaxed, couple of dogs in the frame, and either Keith or Marlon is holding…a large pink parrot toy with the beak broken off?
That photo is from his autobiography “Life.” KInd of neat seeing Keith as Paterfamilias.
That’s funny. I was going to use Dream Theater as an example of a band that met up later. I knew about the Berklee College connection but was unaware that some of them grew up together.
Radiohead
Another good London connection - not so well known - is the Davies brothers were at school with Rodney Stewart. Ray and Dave went on to form a decent little combo themselves though Rod was never in a band with them.
Also, Genesis all met at Charterhouse school, south of London - a bit like Radiohead in that it was quite a posh, fee-paying school.
Old Carthusians everywhere are now tutting at your description of their school as “quite posh”.
The Crusaders (formerly Jazz Crusaders) were all from Houston. I don’t know how early they knew each other, but you don’t get much better in the “talented” department–some GREAT players there.