From the age of two, Emmett started venturing into Erling's backyard and not long after the pair began racing on tractors, riding bikes together and playing croquet.
When Erling moved into a nursing home in 2014, Emmett continued to visit him. He visited his best friend last week, three days before Erling died from heart failure.
His mother Anika said: 'After we told Emmett that Erling had passed away, he was very quiet for a while. The first things he said was, "So we'll just have to wait a really long time. I know we'll see him again in heaven".'