Question: 

A person's sister has married a Shia man and is now following Shiasm apparently.

The family would like to know if this sister would inherit in the event of her father passing away. 

Answer: 

In this time and era, majority of the shias, due to the wrong and unislamic beliefs are considered to be out of the fold Islam rendering them a kaafir and murtad (one who has left the fold of Islam after believing).