Genesis, Chapter 37: Confusion reigns

My husband and I have been studying with Dr. Diane Sharon for years. She's an excellent teacher, in addition to being an old buddy--decades ago, we were members of the same synagogue. She gave such a close reading of the story of the sale of Yosef (Joseph) that I was left wondering who sold him to whom. First, Yehuda (Judah) said (in verses 26-27), "Let's not kill our brother--let's sell him." But it was Midianites who pulled Yosef out of the pit (verse 28)! And it appears to have been those Midianites who actually sold Yosef to the Ishmaelites. Then, just to get us thoroughly confused, verse 36 says that it was the Midianites who sold him to Potiphar in Egypt. Wait, what?