Aynsley comes from good Boro goalkeeping stock with father Stephen a veteran of over 400 appearances for the club and a winner of four promotions with Boro.
Having been with the Academy since Under-9 level, Aynsley has impressed with his continued development and was a regular with the Under-18s before joining the Under-23s.
Aynsley, who travelled with the first team to assist the senior goalkeepers warm-up duties towards the end of the club’s season in the Premier League, made his debut for England Under-19s in October 2016 when he came on as a substitute against Holland.
He joined Darlington loan in January 2018 and made a positive impact with the Quakers for the remainder of the season, starting 16 games in the National League North.
The glovesman has linked up with National League side Gateshead on loan for the season.