This is one messed up family. They are more interested in getting one-up on each other than loving each other; sister against sister, wives manipulating their husband and son-in-law against father-in-law. How are these God’s chosen people?
God still uses messed up people and messed up families to accomplish what he wants to do. I would have picked a family with one man, married to one woman, who remained faithful to each other throughout life and dealt with others in honesty and integrity. God decided he wanted to demonstrate his ability to use broken people. Of course, God chose the better way! He lets us know he can use any of us.