A connection between our perek (and this post specifically) and Parshas Vayigash
At the very beginning of the Parsha - 44:19, Yehuda discusses how Yosef asked them many details about their family. Comments Rashi: "...Why did you ask all these [questions]? Did we ask to marry your daughter, or did we ask to marry your sister? Still, 'we said to my master,' we did not withhold anything."
Thus we see when you do not know the person's family (and they are from a different place), we do not allow a marriage without first investigating the family.
(True, this was 1) before matan Torah and 2) this Rashi says the woman must investigate the man, even though we don't pasken that way - lo huzharu kesheiros linasei lipsulim, but allow me this drash.)