It's called Falling Doesn't Feel So Bad When I Know You've Fallen This Way Too, and it's by BookWerm.

Jack and Ianto are both trans in it, though the primary focus seems to be on Ianto, and just in case, read the tags so you know what you're getting into, but personally I enjoyed it, and I really don't see enough trans torchwood out there, so I thought I'd share!

Falling Doesn't Feel So Bad When I Know You've Fallen This Way Too by BookWerm (JackIanto | complete | 4350 | E)

Ianto has always felt not quite right in his body.

It only became more apparent as he got older.

There's a difference between 'mostly alive' and 'mostly dead'. Sometime it's just hard to remember which one is which, especially when you get right down to the details.

“Hm, imagine if they did,” Ianto said. “Torchwood would have to come out of retirement.”

In one universe, Torchwood Three found the Resurrection Gauntlet early, and Suzie Costello found her darkness and destruction; in this universe, they don't find it until several years later, and that makes all the difference. Suzie picks up the gauntlet, but instead of slowly losing herself to it, she finds a glowing golden goddess - Bad Wolf, and she falls. Oh, how Suzie Costello falls.