Although it hasn't actually been closed (yet!?) Word for two people who are the same age quickly attracted three closevotes - at least one on the grounds that "OP doesn't show any indication of having done background research or having a particular reason for the request."
I came across the question two hours after it had been posed, by which time it had at least half-a-dozen less-than-definitive answers (imho because unlike some languages, English simply doesn't have a common word for the referent, even though it's a common, simple concept).
It took me a while to come up with an answer myself (also less-than-satisfactory, since the OP would obviously have liked a common word), so I hardly think OP failed to do basic research.
I'm left with OP not demonstrating a particular reason for his request. Personally, I get really irritated by single-word-requests where it turns out the only reason for asking is that someone wants a name for a function or variable in his program. Particularly where it's obvious the referent to be named is primarily useful in data processing contexts, not real people talking together. But because we have a preponderance of "techies" here on ELU, there are often people happy to provide suggestions for these highly-localised contexts.
Many, many questions give no indication at all as to why OP would want to ask his particular question. I've rarely seen this mentioned as a problem, provided the question is "answerable".
I'm aware there's something of an undercurrent against single-word-requests on ELU - but I don't really understand that, and I don't want to dwell on it. My question, such as it is, boils down to...
What are the factors constituting justification for posing a question on ELU?
In response to @Feral Oink's answer/comment, I've changed my wording here. I'd like my question to be addressed in a similar fashion to this one about what people consider on/off-topic.
Ideally I'd like very brief answers, each of which describes one possible justification, so people can simply up/downvote each one according to whether and how strongly they agree/disagree with it. Supplementary text for/against each reason would probably be best restricted to comments, to keep things really clear. But feel free to edit any "answers" (by me, at least, as I'll mark them community wiki) to clarify exactly what specific justification it's putting forward.