"Nico," he replied, although he was pretty sure she already knew that. Being polite could lead to some weird conversations which was why he usually didn't do it. Not that he had a lot of people to interact with in the first place.
She was a lot older than him - probably could be his mom, but for demigod kids that wasn't so weird. Gods lived forever and so they had siblings in all sorts of time periods. All through history, really.
"So...we have the same dad."
Awkward conversation starter, maybe, but conversation starter nonetheless.