Usually if we have a toy delema, i ask DS to choose a toy that baby can play with, he thinks that is heaps of fun and will often give her his own toys or one of hers. He does get possesive though and has at the odd time tried to sit on her for fun!! I think the older ones are just learning what they can do with the new baby who is now suddenly moving and crawling and wanting to touch everything!!

Sorry i am not much more help!!