She is the stepmother to the five kids and is 78 years old. She was also (we learned recently) the "other woman" who dated Dan whilst he was married with five kids, youngest 7 years old. Nasty divorce and the kids have always blamed her, but their father made it clear that if they (the kids) wished to be part of his life, they must accept the stepmother. We never knew that until recently.
DH became good friends with Dan through a mutual friend. I liked Dan and tolerated Cindy. We've known them for 20 years and as they've grown older, we've helped them with things around their house, rides to the doctors, etc. But, the past several years they've become quite reclusive and unwilling to share what was going on.
I "got" that I need to leave this alone and I will. They all know the cemetery where the niche is. If they wanted to, they could certainly come out & view it/have a ceremony/whatever.
I really appreciate everybody's responses!!!