They meant to kill him off during season one, but the audience liked him so much, they decided too keep him.
He is also head the the cult King Ianto's Coffee Club, which is trying to replace tea with coffee as the official drink of the UK. Once he comes to power he plans to off Owen, yay.
Someone: Look isn't that the guy who plays Ianto Jones!
Fangirls: *melt in a Janto puddle*