What to do when you buy toys for your kids.
When you buy a toy, don't say "this is for both of you, share it." because it will never happen. Your kids will only fight with each other over the toy. Instead, specify clearly to them for whom (one person only) the toy is bought for. Specify also that it is the new owner's absolute choice whether he wants to lend/share it to/with anyone at any time. Obtaining this understanding is important.
With your subsequent coaching and encouragement, each kid will soon learn to
* let others share his toys
* ask others to share their toys with him
and your kids will have a harmonious and respectful relationship with each other.
NB : Remember ! Buy toys for each kid fairly.