Yes but actually dating your companions isn't a thing. The closest you get is Cass. During one of the ending slides for when you side with the NCR, she kicks the door down that was suppose to be your room to celebrate, but instead of you she just finds some random NCR soldier and sleeps with him instead. Only happens if you're male though.
Veronica is a lesbian but is the worst companion and probably one of the few instances of a poorly written character. Think you can flirt but she doesn't accept your advances. Don't quote me on that.
Funnily enough you can also flirt with Arcade as a women despite him being gay. I'm sure you can imagine how that turns out.
Edit: To add, being bisexual is actually pretty beneficial gameplay wise since you get a flat 10℅ increase in damage against both sexes.