Of note, since I am sure you're curious... I had a 30 minute discussion with both my parents this week. They agreed to ensure the gun is nowhere near the family when we visit, and we will need to tell them in advance if we are coming, in the event he were to have it at home for target practice and we just showed up.
My mother and my siblings are not pleased he has a firearm, but at this point, cannot talk him out of owning one. But we can reduce the risk to our family by keeping it away from them, and it seems this has been done.