Tha Manchin family is a very close, big, powerful family in WV from a very small mining town. I somewhat disagree with your assessment. If, heaven forbid, anything happened to my BIL's, my children would be absolutely devastated, and the closest uncle is 2 hours away, so he isn't a surrogate father. He is just so much fun for my kids when they see him. My children are young, and the loss would be confusing and horrible, not to mention watching their cousins go through losing a dad and the rest of the family's loss, as well. Manchin's loss was in '68, he was 21, watching his cousins (I am assuming because it is a big family). It would be horrible. The mine accident was a terrible explosion with 78 killed, the entire town would have been devastated. I am sure he lost more than an uncle, probably friends and fathers of friends.
Maybe there are other families like this but ordinarily, the loss of an uncle can't possibly be equated with the loss of a child, spouse or parent. If this were so, companies would allow bereavement leave for these relatives but they don't - it is for immediate family only. I am happy the Manchin family is so close. I am sure there are many families that are like this but they are in the minority.