I recently reconnected with a cousin who lives in and owns my grandparent's home. On my mother's deathbed she vowed to her she would add me to the deed of the house. She is now claiming she can't/won't add me because of supposed capital gains taxes. Can someone please tell me if this is truly the case as it was my understanding this would only apply in the sale of the home.

To add. There is no mortgage on the house, it is paid in full.