Complex sentence: George approached Brandi, (who holds a grudge against the Wheetly family) to help him, and Brandi then approached Rachel both of whom manipulated Carson into believing that Ted murdered his mother so they could get his assistance.
Split into simpler sentences: George approached Brandi, (who held a grudge against the Wheetly family) to help him, and Brandi then approached Rachel. Rachel and Brandi then manipulated Carson into believing that Ted murdered his mother so they could get his assistance.