Genesis 28:9

So Esau went to Ishmael and took Mahalath the daughter of Ishmael, Abraham’s son, the sister of Nebajoth, to be his wife in addition to the wives he had. (Genesis 28:9 NKJV)

If we are not obedient to God, we will always try to be good enough on our own strength, our own ideas, our own merit. And we will always fail. I'm sure that Esau's third wife did not make matters better for Rebekah. It probably caused more headache for everyone. Sin does that. It not only affects the sinner, but also everyone around the sinner. I'm sure we've all been affected and hurt by people we love making their own decisions about their own lives.