I think you give your brother too much credit compared to yourself. I saw a pic of your brother. He was very lean, but rather thin. He was more muscular compared to the average untrained person, but not excessively so. The fact he has a low bodyweight, while possessing decent natural strength, allows him to do well at things like push-ups and chin-ups, but if you put him on the bench presses, ovrhead press, etc, etc, etc...he would not do so great.
You likely possess just as much or more strength than him, but your extra bodyfat porevents you from excelling at bodyweight type exercises. On the other hand, you probably beat him on gym lifts. So, does he rea;;ly have a more "incredivle" body than you? it depends on how you define "incredible". if by incredible you mean very lean with decent musculartyure, but still rather thin, then i guess he would, but if someone defines incredible as possessing massive absolute strength regardless of bodyfat, then he wouldn;lt be very incredible at all. i think you sometimes look at people who are lean as having somethiong special, only because you struggle with bodyfat, but there are plenty of very lean, weak guys out there who would love to have the natura srenbth you do. get my point. We always want what we don't have.
I'll tell you a short story. When I was about 23 years old...still life-time drug-free, could bench 400 for a single, and had about 10-12% BG, there was guy...at a drunken party...who flat-out told me he would love to have a body like me. I, on the pothr hand, had been thinking the enture night that I would love to be like him. This guy was a true freak of nature. Until this day I have no personally known anyone like him. He was about 6'5...365 lbs...and NOT obese! This guy looked similar to Andre the Giant, but he did not have gigantism like Andre...he was healthty and had normal pituitary function. The guy had a enormous frame and insane natural strength. He could bench 500 lbs with 2 months of training..and had maybe 25% bodyfat. 25% at 365 lbs, drug-free???? That is straight up nuts!
Back then I was obssessed with size & strength and was in awe of this guy...and the thing is, he couldn't care less about his sise or strength. He said he would have done almost anything to look like me. He hated his body. He said he couldn't get a girlfriend and just wanted to look normal. I, on the other hand, was 6'1, 230 lbs, with an athletic build. He envied me...and I envied him. I could not understand how he could not see how rare he actually was, while there were a million people like me.
The point is that the way we see things is often dependent on the hand we were dealt.