Which action happened first?

1. Their train had left by the time we got to the station. ✅ 2. I had gone to bed before my sister came back. ✅ 3. After we had cleaned the house, we went for a walk in the park. ✅ 4. Ken had already had breakfast when I got up this morning. ✅ 5. I had met Kate’s brother before he came to our school. ✅ 6. We had done the washing-up after all the guests had left. ✅