While there are people in my tree who lack enough information for me to find their ancestors, most of the people I have documented have the opposite problem: too much information. Although primary source information usually corroborates with other primary sources, even that may seem to fail at times. Usually there is a reasonable explanation for conflicting evidence, such as two people with the same name living in the same area, and further information will often sort them out.
It is the secondary sources with their derivative facts which most often produces conflicting evidence, and the reason is usually some kind of human error in the transcription. Again, comparing it to further information can usually sort out the facts from the confusion, but only if one has a way to evaluate each bit of evidence.
Early settlers in America often moved from their original place of landing, but they did not frequently change either their religious affiliations, or their occupations. The names of their children would remain the same except where a daughter changed to her married name, and frequently her husband's name will be found with her father's name in the local military or land or church records.
Wills are wonderful primary source documents which often reveal family relationships and married daughters, but since the eldest son was frequently given the home farm (as well as the care of his aging parents) he might not be mentioned in a will, as he would already be in possession of his inheritance.
This week I read an article summing up the kinds of proof to be found in genealogical records, and how to evaluate it, what weight to give the evidence. Written by Michael J. LeClerc and found in the latest issue of Mocavo News, his research tips, "Sources and Information and Evidence, Oh My!" also includes an excellent flow chart diagram.
I recommend it for anyone doing research on their family tree, as a way of sorting out the relative significance of the records they will find.
For those who wish to delve a little deeper, I recommend the classic "Evidence! Citation & Analysis for the Family Historian" by Elizabeth Shown Mills.