It's always been hinted, if not outright stated, in Paige's Story that the Janes in the story are every bit as romantically and sexually active as the humans. As Fer noted, people aren't going to make hyper-realistic humanoids and not want to screw them.
It's true. So, how do you deal with that? The Janes are basically human in almost all aspects save for construction, which means they can experience attraction and fall in love. Now, when I first started writing this back in the early 2000's, the relationships were all very, very straight. This doesn't make any sense when the people in those relationships are sentient machines. It makes no sense for a Jane to just be straight. They don't have the biological factors that humans do that would influence something like that. They don't really have biological anything. They're machines. Everything from their skyn, to their organs, to their...um...bits... is manufactured. Under their skyn is all metal and wires.
So, when they wake up, they don't have any of that biological feedback to tell them, "Hey you like men." or vice versa. They aren't affected by social stigmas surrounding non straight/cis relationships. Which brings me to the bit of info you were all just dying to know... What are they? Well, if they are going to be sexual beings in my world, it would make the most sense for the Janes to be pansexual.
Being machines they also experience attraction differently than most humans. It's rarely ever a physical thing-- yes they do recognize the human standard of what is considered attractive, but it's like such a
This is all very over-simplified, and I apologize about that. Gender and sexuality is such a big and wonderful rainbow that it's hard for me to properly articulate what I'm trying to say. So... I'm just going to break it down to the basics: In my universe the Janes are pansexual. Fer's relationship is straight presenting. Nix's is gay presenting. That could have easily not been the case. Hell, Fer could have very easily had feelings for his old friend, Hem from Rho squad. We don't know if he ever did, but we do know it was possible.
Look, I decided to dedicate an entire, rambling, blog post about this subject because as the series progresses, we're going to see a lot more of these relationships and meet characters who fall in different places on the gender identity spectrum, and that's a thing that needs to be shown more. Books, TV, and movies have really come a long way with depicting the variety of genders and sexualities, but there's still a long way to go until it's considered a normal thing to see.