"I put something in my tree if three sources agree." I see that kind of statement on a regular basis--implying that "three" is somehow a magic number. Analysis of information is not quite that simple. Might does not make right. Three sources can easily agree if the information was provided by the same person, regardless of whether they were correct or not. John Trautvetter's church record of his marriage says his wife's maiden name was Franciska Haase. The county courthouse record of the marriage indicates his wife's maiden name was Franciska Haase. And his wife is living the the Haase family shortly before her marriage as their child.
Problem is that Franciska was not the child of Mr. Haase. He was her step-father.
There is no "magic" number of sources to make something "right."