Can i buy out my sister share of land in ny for the value .My brother in law is 80yrs Can judge force him.

You will need to provide more information. Now that your sister has passed away, it is necessary to know of she left a will or whether she died before one. If there is no state the law Will probably assign her estate to her husband. Until her assets have not been distributef you can't buy out anyone. After the probate proceedings are finished it is a matter of property law. Additionally, if any debts were left that must be paid first.