She won’t let me see my sick sister

My wife and I are in our 60s. We have been mostly happily married for many years but I am increasingly worried about our relationship with my sister and her husband. They are in poor health but, because of incidents in the past that my wife has exaggerated and misunderstood, she refuses to visit them with me or even talk to them. I have sensitively broached the subject of visiting them without her but I am subjected to rages or the silent