@FloraRose Went thru same growing up. My sibling was diagnosed as ASPD (aka psychopath) so that explains the cruelty. He wasnt diagnosed until in his 40s but still...
I noticed whenever I was a kid and tried to have a functional relationship with him my gut instinct aka nervous system would go into overdrive and that feeling of discomfort you describe would hit. Your nervous system has evolved over 200,000 years to protect you from danger. Someone in the youtube comments of dr ramani's channel said the wise words "your nervous system rejects them before the heart and the head does". They abused you because they chose to. It is perfectly normal to react like that. I noticed you said the words "we live separate lives", that tells me you dont have much to do with them. You also mentioned the word trauma. Our emotions are not to be overcome (you mean like suppressing your emotions so you dont feel them?). Emotions are meant to be felt and processed. Read up on the work by Dr Gabor Mate. If your sibling is still abusing their power over you, you need to put boundaries in place to protect yourself. Remember to find people in your life who treat you well and respect and validate you as a human being.