So I have this YA novel... well, I think it is YA because if it's not then the genre is non-existent. I have six main characters, two of them below the age of 18, but the other 4 between 18 and 25. Would this still be considered YA? Or am I treading into the waters of adult fiction? I feel as though there is still an underlying theme of growing up in the novel, which is why I continue to market it as YA.
There have been a number of age of MC in YA book discussions around here - you might want to search around. But to sum them up, many people think an MC over 18 for an unpublished author would be a hard sell. Others think over 20...some say that in their experience, an unpublished author would have a hard time selling a YA with college-age protagonists.
I personally think that 18-22 year old MCs can work, but don't always, and the older the MC, the harder the sell.
I don't know of any YA debut novels with an MC over 18.
I can think of a few from established authors, but again, not that many, and I can only think of one with an MC over 21.
Not to say it can't ever be done, but it may make it a harder sell to agents and editors.
Are all of the characters equal MCs? If not, and if the older characters are not equal time MCs, then may be less of an issue.
But my take would be a debut novel with one or more MCs over 19-20 will have a much harder time selling as YA than one with MCs 19 and under. And the younger the MCs the more marketable it becomes down to about 16. 16-17 seems to be the optimum MC age for YA.
Now, that all assumes the themes, language and plot otherwise fit as YA...with one or more MCs over 20, I'm not so sure...
~suki