It takes time.
I used to feel the exact same way.
I have a brother. He's 4 years older than me. And I began HRT when I was 21, and my mom and dad were very ignorant to anything trans-related. They were homophobic to a degree, and were very set in their ways, so I was frightened to come out as being trans - but I finally ripped off the bandaid one day after a long lengthy months and months of questioning whether or not I was finally going to medically transition.
My dad came around almost immediately, faltering a little in the middle - asking if I was sure, etc - but eventually came around completely. He was perfect at the pronouns and the name, and all-around no one would have known I was ever anything other than his son.
However, my parents are divorced, my brother is my mother's son and that's where the problem was.
She was happy to "finally get a girl" after my brother, and it was hard for her to adjust to not having a daughter after all.
She said she always knew I was different, and wasn't what she expected in a girl, but she still was upset that I decided to transition. And she referred to my brother as her only son.
It's only been this past year - I'm turning 25 next week - that she finally is able to 98% of the time use the correct pronouns. She always says the correct name. But some of time instead of saying she or he she will just say "that one over there" and points. That is generally her correcting herself before she says "she".
My brother's wedding was a few weeks ago, and I heard a woman come up to her and ask if my brother was her only son(this woman hadn't seen my mother in probably 26 or so years) and she said "Y-NO. I have that one right there" and pointed to me, "And that's his girlfriend" pointing to my girlfriend (whom my mother LOVES).
She came around.
She finally referred to me as another son, rather than anything else.
And she's getting great with pronouns.
It just all takes time. And the older you are, and the longer someone refers to you as one thing, I feel like the longer it could take for some people to begin calling you something different. It's all dependent on the individual, but in my experience, I feel like the people I've had the most difficulty with are the people that has known me since birth.
I choose to think of my transition as a transition for everyone in my life. And you should too. Your brother is accepting you, and eventually when they can't DENY that you're a man any longer (whether you choose to medically transition or not) by you always insisting otherwise, then they will come around.
It is all a process.
Just be you, work on yourself and try not to be jealous.
If I worried about what other men did or what they had and I didn't, I'd drive myself mad.
