I’m convinced, because the Lord Jesus has convinced me of this, that nothing is unclean in itself. But someone may consider a thing to be unclean. If they do, it is unclean for them.
An unbelieving husband is made holy through his wife, and an unbelieving wife is made holy through her believing husband. If that weren’t true, your children wouldn’t be clean. But since it is true, they are holy.