Если притяжательный падеж, тогда вот так:
1) he is George's brother
2)she is Sarah's sister
3) this is Kevin's toy
4) she is Joes's mom
5) he is Sally's dad
6)she is george's wife
7) this is Ann's room
8) this is Coco's dog
9)he is Dima's friend
10) this is Tom's flat