I just learned of a sibling's jealousy ... a brother questioned something he learned about one of my grandchildren ... it was an ugly accounting but the bottom line is ... he's jealous. Therefore, I will look the other way. There is no way I can make this better ... I just consider the source and move on. Like us all, he's on a journey and perhaps, one day, our journeys will mesh and I can share the joy of grandchildren when it isn't such a source of pain for him.
It seems like the simplest way.