"Devan might have bulked up a bit and lost some speed," Cooper said indicating the brothers are obviously tough on each other and it brings the best out of all of them.
Their older brother, Ethan, played Ross Shield rugby like his brothers but didn't progress to the first XV ranks as he made canoe polo his priority sport. Cooper had two years in the Hastings East Ross Shield team during the 2015 and '16 seasons.
He has also represented the Hawke's Bay under-16s and is one of six members of today's first XV in the Hawke's Bay under-16 side. Considering how well Cooper has done in the No 8 role this season fans may find it hard to believe he played halfback in 2017, second five-eighth last year and first five-eighth at Ross Shield level.
"I'm enjoying the No 8 position because you're more involved," Cooper said.
"This weekend we have to treat the semifinal like it's just another game. Obviously they will use their big forwards a lot with plenty of pick and goes. So we will just play our game and move them around," Cooper explained.
Like Devan, Cooper, enjoys the surf lifesaving beach-based sports in the summer and represents the Westshore club. However unlike Devan, who won the Mr Waimarama title in 2016, Cooper doesn't chase pageant king titles.
"That's not my scene," he said.
Cooper is also a canoe polo player and is in his school's top team. While he is aiming for a professional rugby career he is planning to become a physio or physical education teacher so he is prepared for life after rugby.
He is confident HBHS can return to the winning path after their 13-5 loss to Hamilton Boys' High School in their Super 8 final loss a fortnight ago.
'The break has enabled us to freshen up. We didn't do much contact work during the first week but we got back into it this week," Cooper said.
He is one of four Year 11 players in today's Hastings team. Blindside flanker Fraser Taurima-Heperi, winger Mefi Tupou and utility Donovan Godinet are the others.
This quartet as well as halfback Phillip King-Panapa and substitute front rower Manahi Goulton are in the Hawke's Bay under-16 squad.
Prop Jeremiah Tuiatua is still on the injured list and outside back Eldius Oli is unavailable with concussion. Outstanding first five-eighth Latrell Ah Kiong will be given until kick-off to shake off a niggly injury.
Should Ah Kiong withdraw captain Jordan Thompson-Dunn will move from second five-eighth to the pivot role, Elijah Mataira will play in the No 12 jersey and Hoera Stephenson will replace Mataira on the subs bench.
The full HBHS team is:
Mercedes Hodge, Joeli Rauca, Andrew Hayward, Jordan Thompson-Dunn, Mefi Tupou, Latrell Ah Kiong, Phillip King-Panapa, Cooper Flanders, Daemon Brough, Fraser Taurima-Heperi, Julian Goerke, Emil Crichton, Mosese Fineanganofo, Jacob Dorward, Tini Nu'u. Substitutes: Forwards, Manahi Goulton, Josh Folau, Connor Wadley, Donovan Godinet, Arama Kite. Backs, Charlie Varcoe, Elijah Mataira.