Doesn't accept "his" or "her" when unke can be both. The ke is for the apples, not the owners...
My point might be wrong but as far as I could understand by now they usually use उसका -type pronouns (or whatever starts with उस..) to express singular reference (like "he" or "she"). And उनका (or whatever starts with उन..) is used in cases when we talk about plural reference (like "they"). Maybe someone more experienced can share their point.
Oh sorry, I put "Their apple" as an answer thinking they were polite and respectful to the apple, silly me, apples dont deserve rights, sorry
Shouldn't their apple be correct? After all it's written the same in both plural and singular.