(Spoilers for all of Torchwood and 'Torchwood- The Lost files: House of the Dead'. Ages may or may not be canon.)
When Ianto Jones was seven, he swore that he would never fall in love. He decided this after his crush, Suzie Michelson, laughed at him when he offered her a flower.
When Ianto Jones is seventeen, he's arrested for shoplifting earrings for his first girlfriend. He realizes, as his mum is yelling at him, that he didn't even like her that much.
Ianto Jones is twenty when he meets Lisa; beautiful, kind, lovely Lisa. He is twenty three when he admits that he loves her.
He is twenty six when he watches her die, no longer the loving Lisa she used to be.
He is also twenty six when he starts shagging Captain Jack Harkness.
Three years later, Ianto lays in Jack's arms and wonders what the hell he is doing. He had promised himself that it would only be sex, but the fluttery feeling in his stomach said it wasn't just sex.
Ianto Jones is thirty when he figures out that he loves Jack Harkness. He spends the next year trying to figure out what he should do about it.
Ianto Jones is thirty one and dying when Jack refuses to say 'I love you' to him. He dies thinking he has made the biggest mistake of his life in trusting Jack.
Ianto has been thirty one for three years when Jack finally tells him that he loves him. Ianto grins and seals the rift, returning to the darkness with a lightness in his heart.
His Captain loves him. That makes it all worth it.
Ianto Jones is seven when his heart is broken by Suzie Michelson. He swears he'll never fall in love.
Ianto Jones is thirty one when he dies (again) for the love of his life.