For those in the Torchwood fandom and/or Jack-lovers: go read jbs_teeth's What Happens in a 100 Lifetimes. I liked it well enough the first three chapters, but the last ties everything up absolutely brilliantly. It's about Jack's thoughts on various people he's love over the years, and the impact they've had on his life.

And, for those wondering, the story even checks the omnisexuality box. Three human men ( including Ianto ), two human woman, and alien woman. They aren't the only lovers Jack has, but they all relate together - though not genetically.