For me disown seems a stong term, just the same, I'm thinking about where Paul said to excommunicate the person in aggregious blatant sin. Continuing as-is can give the impression we're all OK about it.Dis-own your children? Is that even scriptural? Aren't we supposed to love rather than condemn. Just loved but didn't condemn.
On the practical level, as not all my family are Christians, I've found that voicing my view, my understanding of the Bible, well, suffice to say it wasn't necessary to disown anyone, they wouldn't talk to me!
It was over 10 years that my little sister would speak with me after my wife and I took her to dinner to share the Gospel with her. It was pleasant, reasonable, loving, and she rejected me along with Christ. On a side note, I realized towards the end of my little talk that the whole restaurant had gone quiet as everyone was listening. I can't wait to find out what happened that day!
On a question like this one, I don't know what I would do, but I would trust that God would give me the direction were it to become an issue in my life.
Much love!