I have had several do this. It always seems to be around the 2.5 years old age.
I make sure everyone knows that the toys are MY toys and I'm happy to share them with them. If kids fight over a toy in my house then the toy gets put away and no one plays with it. If someone is hoarding toys and they refuse to share then the toy is taken away.
They learn really quick that if they're not willing to give up the toy they're trying to hoard, no one gets to play.