Gentle, gentle YTA.

My sibling also does not like being in photos. They have had some self image issues over the years. We have discussed this with my family very firmly.

Now we only have photos that we all feel comfortable with. My sibling is also taking steps to feel better about their appearance at this time.

Change starts with you. Advocate for yourself. You said you endured the photos at the gathering- don’t. You need to speak up when you’re uncomfortable, and you need to get some help (be it talking things through with a good therapist, new clothes, or other care items) to help you feel like the best version of yourself you can be.