It can be very tempting to use other people's work when finding common family branches that take you back a generation or ten. The internet has made this very easy through services such as private genealogy sites, MyHeritage, and Geni, but are you doing yourself a disservice?
1. Sources
One of the first things you should look for in other people's work before using it in your own work is whether it is referenced. And if it is referenced, where is it referred to? There have been many cases of family trees that have been established as truths, based on oral traditions in the family, only to be disproved when someone takes the trouble to look for written sources.
2. Dates
The work you are looking at and want to copy may have been copied from countless other people’s work and uncritically copied into your own work. If you take a closer look at the years and dates, do they seem likely? Could it be someone who was 105 years old when they became a parent, or 5 for that matter?
3. Blank generations
In the search for the famous ancestor, some people choose to skip a generation that cannot be documented. «It must be the grandfather who was born 70 years earlier, he has the same surname,» it's easy to think when you go back a few hundred years. Information after such blank generations in the family tree should be taken with an extra large pinch of salt, or discarded completely.
4. Place of birth vs. year of birth
Even though our ancestors were often able to move around the country (and abroad) to a surprising extent, the distance must have been manageable in reality. If you find a mother in a census somewhere and then see one of her children being born on the opposite side of the country two days later, the alarm bells should ring again.
5. Nobility?
In fact, there are fake noble families out there that have been made up by those who have needed it. For example, the «Den norske BRATT-ætten» has been used by many in mid-Norway despite the fact that it has been labeled as fabricated for the past 30 years.
