Complex sentence: Early Reformed adherents settled alongside Lutheran, Brethren, and sometimes Anabaptist/Mennonite neighbors; some Reformed congregations in Pennsylvania formed union churches with Lutherans, sharing the same building but operating as separate entities, although they frequently shared Sunday Schools and occasionally ministers.
Split into simpler sentences: Early Reformed adherents settled alongside Lutheran, Brethren, and sometimes Anabaptist/Mennonite neighbors. Some Reformed congregations in Pennsylvania formed union churches with Lutherans, sharing the same building but operating as separate entities, although they frequently shared Sunday Schools and occasionally ministers.