Both excellent long distance runners as well as footballers in their primary school days, Tyler and Jack have tended to be viewed as a pair.
Though they have taken strength from each other's presence as they have come through the ranks - initially at Manchester City before switching to United in 2023 - they are very much individuals, which goes beyond the beard Tyler grew which helped to tell the difference between them.
Often picked together in United's midfield at Under-21 level this season, Tyler is more of a number six or number eight. His brother plays slightly higher up the pitch.
Darren, capped 80 times by Scotland, but who never played in a major tournament, has evidently been a key presence in shaping their respective careers. Time and again the duo are described as having similar traits to their dad, including, simply, "being really good lads".
However, Fletcher senior was also keen to ensure his sons progressed beyond under-18 level before he agreed to take the job this season to avoid any conflicts of interest.
Those who know Tyler say is he a confident, driven young man, but equally very low maintenance. "Polite and conscientious" is how he has been described.
Physically, it has been noted he has settled down, which is key at an age where development is not complete and can come in surges.
Professional development has also been impressive.
Twelve months to the day before his international bow, Tyler was making the second of two brief appearances for United in the final game of their controversial post-season tour of Asia.
It says plenty about his assimilation into the senior ranks, and his performances in his frequent call-ups to training sessions by Carrick that Tyler was invited to the end-of-season squad dinner, arranged by skipper Bruno Fernandes, after the Forest game.
United coaches feel in addition to his stamina and athletic prowess, which they expect to grow as the months go on, Fletcher's all-round game has improved significantly.
They believe his ability on the ball, vision and understanding of the game means he will become more versatile as the years go on.
Fletcher has slowly been getting used to playing men's football.
In the first half of the campaign, it was for the under-21 side at places like Brackley, Solihull and Tamworth in the National League Cup, or Lincoln, Barnsley and Notts County in the EFL Trophy. The appearance at Brighton alongside Shea Lacey confirmed Carrick, who has watched numerous Premier League 2 games in person, views him as one of the academy players most ready to make the big step up.
A week ago, the next stage for Fletcher was expected to be as one of the youngsters who will form the core of the group Carrick will take to Helsinki for United's first pre-season game against Wrexham on 18 July, the day before the World Cup final, and the trip to Rosenborg in Norway the following week.
Those plans might have to be shelved. Fletcher may have other, even more pressing commitments in July now.
"The best day of my life," was how Fletcher described his first-team debut in February. That might have dropped down to number two in his rankings.

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