Questions & Answers about آنها کتاب را در خانهی خویش خوانده بودند.
Why is there a -ye connecting khāne and khish?
That is the ezafe! Even though khish (one's own) is a reflexive pronoun, it acts like a modifier here and connects to the noun (khāne) using the ezafe, just like khāne-ye khod. Because khāne ends in a vowel, the ezafe takes the -ye form.
Could we attach a personal suffix to khish here, making it khisheshān?
No, unlike khod, the literary word khish does not usually take personal pronoun suffixes. It stays simply as khish regardless of whether the subject is I, you, or they. The subject ānhā already gives us the context that it means their own.
How would this sentence change for everyday conversation?
In spoken Farsi, you would use khod instead of the formal khish. The phrase would typically become dar khāne-ye khodeshān (in their own house).
What tense is khānde budand and how is it built?
This is the past perfect tense, translating to had read. It combines the past participle of the main verb (khānde) with the simple past of budan (to be) conjugated for they, which is budand.