Colquhoun said the story of the reunion began two years earlier, when he bought a Hearts vs. Liverpool soccer game program on eBay.
He said he received a message from the seller saying his purchase was being refunded, and the seller then explained why -- he was the father Colquhoun had never met.
Colquhoun said the eBay purchase led to his getting to know his father's side of the family, but the COVID-19 pandemic got in the way of his meeting his sister until Monday.
"We laughed, we cried, and we shared stories. It felt like we'd known each other our entire lives," Colquhoun tweeted. "I was extremely nervous, but it was an absolutely beautiful and life affirming experience."
He wrote that he found he had a lot in common with his long-lost sibling.
"We talked about our lives and experiences, which seem remarkably similar. Erin studied at Glasgow School of Art, whereas I attended Edinburgh College of Art.
"The trepidation is still there, but I'm really looking forward to meeting the family members I've yet to meet," he said.