Complex sentence: They encounter and team with Templar husband and wife, Wesley and Aveline, but either Bethany or Carver, Hawke's sister/brother, is killed (depending on Hawke's class type).
Split into simpler sentences: They encounter and team with Templar husband and wife duo, Wesley and Aveline. Additionally, either Bethany or Carver, Hawke's sister/brother, is killed (depending on Hawke's class type).