3rd Rock from the Sun - Season 4 Episode 11 Dick Solomon of the Indiana Solomons

An invitation arrives in the mail from an 'Aunt Florence', inviting 'Richard Solomon' to attend a Solomon family reunion in Indiana. This is obviously a mistake, so Dick phones Florence to set the record straight. Upon discovering that Richard is so estranged that his family wouldn't recognize him anyway, he decides that the aliens could do with some roots and accepts the invitation. Upon arriving, however, it becomes clear that the only reason the real Richard is estranged is because of an old family fallout - and it hasn't burned out yet.