Often, on the records, the people listed as "witnesses" to a wedding or "informants" of the information (births, deaths) are close family members. Pay attention to these people. Search them out. Knowing more about them will help you to know more about your ancestors.
For example, my great grandmother's wedding registration lists her sister, Janet, as a witness. This particular sister was one of three sisters that my great grandmother had. But she was the oldest sister and the eldest child. My gre