My husband and my sister?

My husband is an oncologist physician (cancer doctor) and he has been a good part of my personal family (growing up without parents and siblings, my mom and dad see him as kind of their son). He is a very nice man and has done a lot of contributions and research to cancer without taking any money. He has done checkups for my parents for free. However, my sister has asked to receive a gynecological exam for cancer, and a week from that other checkup he will give her a mammogram and do some bloodwork to detect cancer as it runs in our family. My husband has never cheated and is very religious. However, I feel a bit tense of him physically checking my sister (especially the vagina and breasts). There will be other nurses in the room though. I get a little insecure sometimes when I also see him with other female doctors at the hospital where we work in (I'm a nurse). Our family goes to him for cancer checkups frequently as he is a world acknowledged physician and is one of the best in the nation, so they wouldn't have anyone else. Plus, obviously my parents and sister know him as he is my husband. Am I taking this too far? Is it normal that I feel a little agitated about this? No one in my family has brought it up, and they're okay with it...your thoughts?