please bear with me while i work on this. itll be done eventually i promise.

Many times I have seen people online claiming that Ianto is not actually bisexual despite there being plenty of evidence pointing to the contrary. This essay will hopefully be a good resource to prove them wrong, with counter-arguments to the common misconceptions surrounding this topic backed up by my analysis of various scenes from canon and quotes from interviews with the creators.
Without further ado, let's get started.

"IANTO ISN'T BISEXUAL BECAUSE HE TELLS HIS SISTER HE ISN'T ATTRACTED TO MEN."

This is one of the most common arguments used by people who do not believe Ianto to be bisexual, and they usually completely forego the context that the entirety of Children of Earth gives to this scene and Ianto's relationship with his family in general.

As soon as Ianto enters his sister's home, we can see the contrast between them in everything, from their jobs — Ianto's high-paying (although secret) government job versus Rihannon doing small jobs from home to care for her children — to their clothes and mannerisms. Rihannon quickly complains about Ianto never bothering to visit or even share anything about his life since their father died, and through Children of Earth Day Two and various extended universe stories, it is hinted that Ianto endured much abuse at the hands of his father and quickly became even more alienated from his family when he started working for Torchwood and was forced to lie to them about everything in his day-to-day life.

As Rihannon sits down with Ianto to catch up, she mentions that one of their neighbours saw him in town with a handsome man. She pushes Ianto to tell her more about this despite his obvious discomfort, their conversation going as follows:

RHIANNON: Susan on the corner was in town and it was her anniversary, so they went to that posh French place in town by the memorial, and there was you.
IANTO: So?
RHIANNON: There was you, having dinner with a man.
IANTO: So?
RHIANNON: Having dinner with a man in a restaurant.
IANTO: So? You have dinner with Tina.
RHIANNON: Not in town. Susan said he was gorgeous. Like a film star. Like an escort.
IANTO: He's my boss.
RHIANNON: She said it was intimate. I said, well, he's had girlfriends, and she said, w ell, no girl was getting her feet round that table. No chance. Have you gone bender?
IANTO: Mica's hearing this.
RHIANNON: She's not bothered. Her friend Sian's got two mothers. Go on. You never tell me anything these days. Dad died, that was it. You were off. You couldn't wait. Like I did something wrong. I didn't, did I?
IANTO: It's not that. It's my job. It's difficult, it's. He is very handsome.
RHIANNON: No.
IANTO: Now stop it.
RHIANNON: You're kidding me. Really, though? Really? Christ almighty. He's nice, though, is he? Is he? Oh, my God. I mean, since when?
IANTO: It's weird. It's just different. It's not men, it's just him. It's only him. And I don't even know what it is, really, so. So I'm not broadcasting it.