"Their children live in the house."
Translation:उनके बच्चे घर में रहते हैं।
Uske = His/Her
Unke = Their
So, uske is used when you're talking about a single person and unke when you are talking about more than one person.
However, when you are talking about a person older than yourself or in a position of authority, you should use the plural form as a way of showing respect. So, 'unke' would be used for them.
The difference is similar to that between the words 'this' and 'that' in English.
'Unka' is used when you are talking about people who are (physically or figuratively) far away while 'inka' is used when you are talking about people (physically or figuratively) nearby.