In hindsight, it makes perfect sense.
Duncan Cumming and Ron Cole grew up as best friends in Ottawa, Canada, in the 1950s, but it wasn't until 2013 that they finally figured out why they shared such a strong bond as children. Turns out the two boys, who were each adopted and raised in separate families, are also biological brothers.
Ron Cole, left, and Duncan Cumming, right, were friends in the 1950s.
The two were connected by a group called Parent Finders Ottawa, a Canadian nonprofit that reunites family members separated by adoption.
Though they both moved away from their hometown and haven't spoken for nearly 60 years, they're planning a reunion in Ottawa next month, reports the Ottawa Citizen.
Cumming told the Citizen that and Cole looked nothing alike, so they never suspected they were actually related.
"We were chums in public school for about two or three years, not knowing that we were brothers," Cumming said. "It’s unbelievable.”
Unbelievable, indeed -- but not as rare as you might think.
In January, two girls who became friends while attending Tulane University found out they were also half siblings who shared the same sperm donor for a father.
And in 2012, a chance encounter between two boys at a pool in Missouri turned into a family reunion after a mutual friend pointed out how similar they looked. A subsequent discussion between the two revealed they shared the same mother.