Most of us have a few ancestors who had more than once spouse. Sometimes it can be tempting to ignore those “other” spouses of our ancestors– the ones from who we do not descend. However, this may only serve to hinder our research. Many times a subsequent spouse will be a sibling of the first spouse, or perhaps a former neighbor from the old country or the old neighborhood. I even have an uncle by marriage who after the death of his first wife married her niece, thus making his children half-siblings as well as first cousins once removed.
Also remember that records of your ancestor’s “other marriages” may provide more details on your ancestor than did his marriage to your ancestor, particularly if those other marriages took place much later than the first marriage, or in a location that kept better records.
I even have one ancestor where I descend from both their spouses. But that’s another quick tip!