Nephew thinks he is gay, sister doesn’t want him to say anything

My nephew is 11 yrs old. In this time frame, he has gone through his fair share of identity crisis’s. My sister and her husband are divorced. They are not on good terms, and my culture is not as progressive as most, and it’s still very frowned upon to be “different”. Now that I have set the stage, I am looking for some insight. My nephew has told a few family members that he thinks he is gay. My sister told him to stop talking about that and to never mention it to anyone. He is so distraught…my sister is extremely volatile and takes everything as a criticism to her parenting. Also, she is going to get “blamed” for my nephews lifestyle or as I like to refer to it as his “magic” I know I have to speak to her, but I don’t want to damage our relationship. But at the same time, my nephew is suffering, and I want him to have the support and the resources to help him find his true self. Has anybody been through this?