Byron was cut by the Swans during his second season, after the club said he was "struggling for some time with the commitments and demands of AFL football".
These "struggles" included being late for training and missing sessions.
But following his first session with the SUNS on Monday, South Australian Tim said his brother's mistakes had been a great teacher.
The pair played together the past season at Woodville West Torrens, with 18-year-old Tim in his first year of senior football.
"He made a mistake being there and he said 'once you get up there, just do everything right'," Tim said of Bryon's advice.
"Listen, respect everyone else around you and you will go well. He said don't follow in his footsteps."
Byron is still just 21 and a big influence on his younger brother who has a huge vertical leap and ability to play all over the ground.
"Being at the Eagles and going up to senior football with him pushed me along," Sumner said.
"Doing extra training sessions with him just to get ready for the draft and the Combine and he has been really good."
It's a process that saw the teenager vault into draft calculations after playing amateur football in 2010.
He was taken with Gold Coast's second selection with pick number 55, but said he thought the boat had sailed on his chances.
"I spoke to my manager and he had a lot of confidence in me going in the 40s, and I thought I was going to go in the 40s as well," he said.
"But my confidence started getting lower as the numbers started getting higher and as soon as it come up I was pretty excited."
"I had a couple of moments to myself and started to think 'it's a new lifestyle and I've got to get ready to fly out'.
"Leading into the draft I wanted to go interstate just to break away from the family and become a lot more independent. Gold Coast … couldn't ask for a better spot."
