Respectfully (genuinely!!), his behavior could merely be dysfunctional, rather than “not normative,” “atypical,” or “abnormal.” Some families are just plain dysfunctional. Our VI has said Barbara’s son gave her a lot of trouble, or problems, or something (don’t remember the exact wording). The fact is, Barbara may have forgiven her son for his past transgressions (whatever they were), but Robert might not have. Robert might not have felt MS deserved to hear from him.
If Robert didn’t have a relationship with Barbara’s son (or had an estranged relationship with him - Michael has made it clear he doesn’t like or approve of Robert), Robert genuinely may not have cared one iota if MS ever found out. There are a lot of f’d up families and extended families out there. Heck, even Barbara’s brothers are estranged from one another. Has her missing status resolved that estrangement? Why should we expect it to resolve this other estrangement between Robert and Michael - that admittedly is assumed on my part..
I have a sister that only speaks to our 85 y/o father; none of my siblings has her phone number or has spoken to her in more than ten years (the rest of us communicate regularly). When the time comes, I know I will not be the one to try to find her to let her know when our dad passes. Harsh? Atypical? Not normative? Or just plain dysfunctional? Maybe if you haven’t lived it, you can’t understand it. I say my husband’s family is so normal they are abnormal, but that is based on my familial experiences. I know we are not supposed to share much personal information but this seems relevant experience so I hope it is not outside TOS.