A parent has a child who is unfaithful and living in another state. Is it wrong based on Ephesians 5:11 to visit that child and spend weeks or months in the same house?
If the child is a fallen Christian, then "But now I have written to you not to keep company with anyone named a brother, who is sexually immoral, or covetous, or an idolater, or a reviler, or a drunkard, or an extortioner--not even to eat with such a person" (I Corinthians 5:11) applies.
The question should be: what is the purpose of the visit? Is it to teach the child? Is it to give support to the grandchildren? Much can be done without giving the impression that you no longer care whether a person is a Christian or not. If the visit shows support for the child in his fallen state, then it is wrong.
Thank you, sir.