The only other person he's slept with is Alfe and that relationship is ,,, complicated.
His whole relationship with sex itself is complicated. He doesn't despise it and he's not asexual, but his experience with it so far is less that stellar. Getting off for him is a big event and really emotional and draining and kind of embarrassing to do it in front of other people, but he has a hard time climaxing on his own due to his reluctance to really touch or look at his self 'there'.
He's really dysphoric and the whole 'dressing as a robot thing' is mostly to cope with that (he also thinks its really cool). He's mostly male, but not all the way. He's more of a demiboy, but like a subcategory, like "roboboy".
You could also say he's otherkin (to robots) but he wouldn't use that term. He doesn't like its origins and culture too much.
Alfe sometimes has problems with the whole trans thing. He says stuff like " born a girl" and "has girl parts". Horace calls him out on it but Alfe is Alfe.
Alfe sometimes acts really gross too. He'll grope Roba or try to touch his chest (though there is not much to grab with Roba's ultra fancy robo binder). Roba's conflicted, because he (secretly) likes to be touched and like intimacy, but he knows Alfe is doing it because he's dfab.
He occasionally sleeps with Alfe. It's always a rash decision with plenty of regrets later. Roba has a lot of weird feelings about it. On one level he feels like he's being used and taken advantage of and he should tell someone (especially) the times he get hurt/gets bruises.
On another hand he feels like he's the one taking advantage of Alfe and he's the one in control. He feels like he took advantage of him and slept with him just to suite his needs and later he can go back to treating Alfe how ever he wants. It gives him a big power rush, but he low key feels guilty the whole time.
It's awkward, messy, sweaty, sticky, a bit rough, and a little uncomfortable.
The first time he didn't get off though because they were under prepared (without lube or protection) and it mostly just hurt for Roba, due to him being out of practice, nervous, and Alfe being too big for Roba.
The second time he didn't get off because Alfe nutted in him and Roba freaked out. He was super sure he was going to get pregnant and die. From embarrassment and Alfe's kid getting way too big inside him (which probably wouldn't in this universe, its just Roba being irrational). He took every morning after and started birth control (which fucked him up with all the hormones. His voice got high and weird and his chest and hips swole) and got a bunch of different pregnancy tests. He also had crazy weird dreams about Alfe bursting from his stomach/womb many times. He wasn't pregnant, but it was still an awful experience. He couldn't tell Horace about it because that would mean telling Horace about sleeping with Alfe and he was not ready for that. Horace was really worried about his at that time though.
The third time he did actually get off. Roba made sure they got condoms and lube together before doing it (though it was still really on the spot). When he did orgasm though it, of course, was one of his big emotional ones. There was lots of yelling and jerking and pulling and name calling and shame was there shame. Once Roba regained himself he was instantly embarrassed, it didn't help that Alfe was really weirded out by the whole ordeal. Roba didn't talk to anyone for a week (except for making Alfe SWEAR not to tell anyone and also make sure he doesn't blab about them getting it on, which he had been doing before, but Alfe needed reminders).
After that it was sort of regular. Not regular as in 'it happen a lot' but that they kind of had the situation down and were ready. Even with Roba's brigade of over emotions.
Eventually Horace did find out and unfortunately it was by walking in on them. It was late at night and Horace was out on a date, but the date didn't go so well, so he came back early and unexpected. He came in the house quietly because he didn't want to wake them up, but he heard them and being the lawfully good moral friend he was he went to go check on them thinking something might be wrong. Then he found Alfe screwing Roba in Roba's twin bed in his open pajamas, with Roba's binder off and all. Which all came out of left field, with Horace having super Sunday school vision goggles on 24/7, he did not see this coming at all and sent a shock to his placid sensibilities. Roba first claimed Afle forced himself on him, then pretended he didn't know what was going on, to finally forcing everyone else out of the room and crying. At first Horace believed Roba's first story but after listening to Alfe's story about this happening multiple times and Roba's big pregnancy scare he realized that Alfe was right. Eventually it was sorted out and everyone accepted this new fact of life.