Answers:
13. Who are they?
14. We lads were at the cinema at the same time as them.
15. Between you and me, I know all about Sue and her.
16. He is almost as big as me but smaller than her.
17. Her sisters are smaller than us but she is taller than I.
18. You must choose between them and us.
19. You and I could do it, but not you and him.
20. It appears to be her about who you should worry.
21. She and I are twelve years of age.
22. Her cousin is younger than her or me.
23. Was it me whom you saw there?
Hope this helps :)