Rebecca,
Family trees with valid sources such as vital statistics--marriage, birth, death, family Bibles, wills, deeds, census records, works by bonafide authors. Currently working on a profile that has the same name for about twenty people, e.g. John Smith who can be a brother, son, uncle with that family same name, John. So to clarify which one married so and so and which one was a brother and who the one left over is--that is the question. Geni has good info but have found errors in my family. Just verify not dismiss. Family trees because grandma said so may not be accurate. In some cases one source does not suit all.
Sharon