In cultures where women take the last name of their husband, it can sometimes be difficult to know (without doing a search of marriage and other records) if a man had two wives with the same first name. This tombstone indicated that Nels Johnson had two wives named Mathilda–one was Mathilda S. and the other was Mathilda P.
Other records do not always use middle initials and sometimes we are not so fortunate to know that there were two wives with the same first name. 1850 and later US census records may list the same first name of a wife, but details about age and origin may suggest the two same-named women were not the same.
If you suspect a man was married to two women with the same first name, a check of marriage records is the first place to look to validate your suspiscion.