Re: Sharing vs. more toys
As others said, if it is a main piece that they both like playing with consistently, I would get 2. If it's more of one of them wants the majority of the blocks and isn't willing to give some to the sibling, I would encourage them to share.
My boys are 13 months apart, so we make sure that we have enough trains and cars or whatever they are playing with that they can both play, but one of them is not allowed to hog all of the pieces just because they want to.
Hi I'm Sara mommy to 4 little Mischief Makers