Quite simply, merge the two IDs, if you are really convinced you are dealing with the same individual / family. Sometimes, you can do this via a "Possible Duplicate" link that appears on the main page. Otherwise, click on "Merge By ID" (under "Tools"). It is usual to work from the ID containing more / more accurate detail. The information from the ID being merged with it is carried across (where fields are blank) so you might have to make additions / changes after the merge (for which you should provide a reason statement) is complete. Finally, make sure any other duplicate IDs (for spouse, children, parents, etc.) are also merged.
It can be a slightly complicated process, so work very slowly if you have not undertaken it previously.
Quite possible ...
Firstly, it is NOT impossible for them to be two (x2) separate and distinct Families - I am not saying they are.
But, in fact, it is quite entirely possible that they are ... I have come across this a number of times.
And, you did not indicate whether or not the Families were from the EXACT same locality.
Secondly, DO NOT even think about "Merging" / "Combining" the Families ... until you have done your due diligence; and, research everything about the Families.
Quite a number of times I have had to SEPERATE, two (x2) separate and distinct Families, that were INCORRECTLY "Merged" / "Combined".
Once, that took two weeks, large Families, almost exact same names, from same County; but, different Localities, just a few Miles apart.
They were "Merged" / "Combined" because of a Census ... it was a real mess, due to later work, following the "Merge" / "Combine".
Finally, take your time, do the research, be certain, before you "Merge" / "Combine".
Just my thoughts.