I listened to a devotional speech from BYU today regarding "righteous desires" [1]. There was a quote that I felt is very relevant for any loved ones who are supporting a spouse/partner/child in their quest to be free from pornography.

“You can build upon his desire, but he alone must initiate the desire.”

The point here, is you cannot force someone to want to quit porn. They must choose to quit porn. However, you can support them in their efforts to quit. They must choose for themselves what they truly want to do. It can be helpful to educate, teach about the delayed consequences of pornography which is especially helpful for children/teenagers (see this post). I'd also encourage the Spiritual damage done by pornography. Teach of faith, God, virtue, honesty, integrity, etc. All of these things can help someone to better understand the choice that is placed before them. But at the end of the day, they must choose to be free from porn.

I'd also add, just because someone relapses doesn't mean they don't have the desire to quit. Help them, encourage their good desires, don't be saddened when there's a bump in the road. There is hope. Given enough time and effort, I believe everyone can quit.

[1] https://speeches.byu.edu/talks/neil-l-andersen/educating-our-righteous-desires/