Here's an example of my sister's sacrificing. . .

She had a partial knee replacement a couple of years ago. My parents had plans to come for a visit about 1 month later. My sister wanted my mom to be there during the surgery, but didn't want to ask, and my parents didn't come. They waited for 1 month. When they arrived, my sister was still recovering from her knee surgery, and her knee was hurting! But my mom wanted to go shopping. (She spends most of her vacations here shopping.)
I knew my sister's knee was hurting, but my mom said, "I think it would probably be good for you to get out and walk." So we went. . .

Partway through the day, I noticed my sister was sitting in a chair outside the store waiting for us. Again, I knew her knee hurt. So when we got in the car, I said, "We can go home now. We don't need to shop all day. I know your knee is hurting." My mom said nothing. Then my sister said, "It's OK." So we continued. Later, I found out that my sister even took my mom shopping and sat out in the car waiting for her.

My mom should have thought about my sister's knee, not about how much she wanted to shop. I felt disappointed in my mom, especially since my sister is the golden child and has done everything in her power to keep that position and have their approval. They do treat her much better than me, but not as good as she deserves.