I got to the point to romance Piper earlier than I was expecting. I didn't know what would happen immediately after and my 7yo son was in the room so I skipped it and chose 'thank you' (I had quicksaved but I apparently quicksaved after that erasing it before he went to bed so I couldn't go back and choose Romance). Will it come up again? Or is there a way to make it come up again?

Try romancing the robot, curie.
I wont spoil it, but ill say the quest and the result is alot more worth it for a female companion than piper. Plus she doesnt "like" genric tasks like lockpicking so her affection meter goes up slower.. Makes it feel like youve done something to earn it. Win-win.

I believe you get more then one chance. You may have to spend more time traveling with such a companion and yet again talking to them frequently. However I do not believe and have not heard else wise that you get a one shot situation per companion. I have just been focused on getting the perks from each companion and have seen Romance or even flirt option a few times but I try to stick to the other dialogue options as to get the perk asap.

As a side note for future reference, there is nothing explicit with the romancing in this game, just romantic sweet talk and fade to black, so no need to worry about ya boy seeing things about the birds and the bees.

Thank you all for your responses. I do plan to romance Curie. It's on my todo list And it's good to know I won't have to worry about the six scenes. There are so many MA games now that you have to be careful about. I do hope the option comes up again. I can see more chances if you fail the romance attempt, but I didn't know if you just stay in the friend zone if you chose not to romance.

Yes, I refused to romance Cait but still got to the highest level of friendship with her, and every once and a while she would do a speech and open up for romance, sometimes even if I was just walking by her in a settlement.

Awesome. Thank you.

Best companion to romance in my opinion that french accent is such a nice change