You know, only in the Witness theology would the claim of anointing be considered "selfish".
Perhaps this man has had a genuine conversion experience, and anointing by the Holy Spirit. I've experienced it, and so has Little Toe. From my theological perspective, anointing by the Holy Spirit is a gift, freely given, and available to all. Perhaps you can get some comfort from Little Toe's story. Perhaps this is the first step in your brother-in-law's exiting the society.
I understand your sister's fear. This means he has no intention of joining her in paradise.