Complex sentence: On the other hand, marriages tend to be between nearby families, and neighborhoods become small networks of direct and indirect affinal relationships with a few further connections of direct agnation or common clan membership.
Split into simpler sentences: On the other hand, marriages tend to be between geographically nearby families. Neighbourhoods become small networks of direct and indirect affinal (connected by marriage) relationships together with a few further connections of direct agnation (relationship through the male side of the family) or common clan membership.