Thank you for your question. I look forward to working with you to provide you the information you are seeking for educational purposes only.
I am a DIFFERENT CONTRIBUTOR.
Your previous contributor was correct in that until the child and mother are actually residing in WV for the 6 months continuously, you cannot file there. Once they are living there, then the issue becomes whether or not the SC court retains jurisdiction on the case, since that is the court where they filed the custody/divorce action in first and they retain jurisdiction over child custody.
Grandparents rights could be a separate action filed in WV once she is living there for the requisite time. However, you need to know that the US Supreme Court has essentially gutted the grandparents rights laws based on their decision in TROXEL V. GRANVILLE (99-138) 530 U.S. 57 (2000). The US Supreme Court has stated that the rights to make decisions for the child are fundamental rights (basic civil rights) of the biological parents and they cannot be interfered with unless the parents are found to be unfit by clear and convincing evidence. So what grandparents rights you get will be based on any custody rights your son obtains in SC in the divorce proceeding. If she gets sole custody, then the US Supreme Court states she has the right to deny you visitation. If your son gets "joint custody" (even joint with her as primary physical custodian), he has a right in the legal decisions for the child and he can decide you should be able to visit with the child and if she refuses, then you can go to court based on your son's decision, with your son (or his attorney) to seek to enforce his decision to allow you to visit with the child.
However, if this case is filed in SC, you have to get the order in SC, because the WV court cannot take jurisdiction away from the SC court even if she is moving and living in WV unless the SC court agrees to relinquish jurisdiction. If the SC court agrees to give up jurisdiction, then you can file for grandparent visitation with your son and through your son's joint custody decision making rights.
These cases get very complicated thanks to the US Supreme Court decision making this a civil right of parents (not grandparents), so you would need to start this now with the SC court in the custody case, where your son has to get the SC court to put in the custody order that he has the right to grant you visitation in his absence and get the SC court to put that in the custody order. Then you can take that SC custody order and file it in WV with a petition to recognize and enforce foreign judgment and if the mother does not comply with the judgment, you can go through the WV court to make them enforce it against her.
You cannot do this pro se, you will need an attorney or your son's attorney in SC to get this started and then to enforce it in WV if you need to, you would need a WV attorney to file the judgment and seek enforcement there.