Complex sentence: Before 1850 the U.S. Census recorded the names of only the heads of households; others in the household were only counted, and if he existed, Beale may have been living in someone else's household.
Split into simpler sentences: Before 1850 the U.S. Census recorded the names of only the heads of households; others in the household were only counted. Beale, if he existed, may have been living in someone else's household.