House Property

Dear! Thanks for the question! Here the Hindu Law is applicable. there are two scenarios -

1. Self Acquired property - If the property is self-acquired property i.e bought by your parents' own earned money, then they can do as they please and cannot be disputed against. They can write a will and give it to anyone they want to without any interference.

2. Ancestral Property - However, if the property is an ancestral property that was devolved on your parents by the virtue of being a successor to the ancestors then they cannot write a will and give the property to the sister exclusively. You can claim your share in the property and dispose of the calculated share as, when and how you please.

Good Luck!

Your Son/Daughter can expect a share only from the property that devolves on you. The share that you get will be divided between your children. 

The grandchildren get a share in the ancestral property only in the event where the class I legal heirs are dead i.e - you and your siblings. So again, it depends on whether the property itself acquired or ancestral and what share do you get out of it.

The query has already been answered clearly and properly.