Are there some "obvious" clues you are overlooking in a document, record, or artifact? If your ancestors had their picture taken on their 50th anniversary with all their children, then it means those children were living on that date. It might be a small clue or a big one depending up the situation. Survivors listed in an obituary can obviously be viewed the same way--just like people listed as attending a reunion in a newspaper notice.
Are there "obivous" clues you have overlooked?