He even helped to train them before they joined, taking the men on exercises in nearby fields around the city.
Every single one of those new recruits was killed at the Battle of the Somme. It left the Rosemount area of the city, where they came from, bereft.
It also left Thomas's widow, who had six children to raise, alone and ostracised.
Elizabeth Young's neighbours blamed her husband for leading their sons and brothers to their deaths.
"I never really knew my granddad," Lily O'Hagan said. "But listening to my granny through the years, and listening to what she was saying about him, she must have really loved him to bits."
Lily still lives in the same Rosemount area as her grandfather.
"At 15, my granddad was taken out of the orphanage and put into the army. The army was his life, it was all he ever knew," she said.
"He used to take young boys to the fields and train them and march them and walk them round.
"Then when World War One broke out, he encouraged them to join up."
Lily said her granny, Elizabeth, was treated like an outcast by those who had lost loved ones.
"Even the shops wouldn't serve them so she always had to go into the town and bring up what she needed," she said.
"She had to take my mother away from school at eight years of age to look after the younger ones, so that she could go out to work.
"She didn't get things easy, she never did but she brought them up and I can say I was proud of her.
"They blamed my granddad for taking the boys away.
"She (Lily's granny) used to always say, 'I know he talked to them, he had them away and trained them around the back but he never put a gun to their head to tell them to do it'.
"When I think back on itâ€¦ all the young women of her age going about, they still looked young, but my granny is sat in a corner with an apron. She never really had a life."
You can hear more about Lily O'Hagan and her family on Breakfast on BBC Radio Foyle on Wednesday 29 June.
When World War One broke out in 1914, Thomas Young, from Londonderry, encouraged other local men to enlist.