I hated him when I was a kid because he instructed me a lot of thingsbossed me around and I wasn't able to deny themrefuse.

I think this is along the lines of what you wanted to say

However we can be goiget along well now,; for instance, we both like coffee and wentgo to coffee events together.

You could split this into two sentences where I used the semicolon (;) but I think since these two are linked it works best with a semicolon.
"we can be going well now" doesn't quite make sense, it should instead be "we get along well now" - 仲が良いという意味です
Since you're talking about the present and (I'm guessing) intend to go to more you should say that you "go to coffee events" rather than "went". If you don't plan to go to more then you could say "we have been to coffee events together".

The two of us have becomen grown maen.

"The" is needed at the start of this sentence. "have been" implies that you no longer are a grown man, so "have become" is more appropriate here.
"man" should be "men" since you're talking about the both of you

I hated him when I was a kid because he instructed memade me to do a lot of things and I wasn't able to deny them(for him).

Another possible phrase with the same meaning: I hated him when I was a kid because he ordered me around.

Instructing someone to do something they cannot refuse = making/forcing them to do it. "Forcing" is more strong, "making" would definitely be used for a sibling relationship.

I would add "for him" if the things he ordered you to do were typically for his benefit

However, we can be going wellget along now, for instance we both like coffee and wentgo to coffee events together.

Some nuance:

We get along = basic form of this phrase to say you are on friendly terms
We get along well = stronger in a positive sense
We get along well enough = stronger in a negative sense, to say you are almost not on friendly terms

A "coffee event" invokes a particularly special function, like a coffee festival. If you just mean that you meet up with your brother to drink coffee casually, you should instead say, "... we both like coffee and meet up at cafes."

The two of us have been grown maup into men.

I hated him when I was a kid, because he instructed me a lot of things and I wasn't able to deny themkept nagging me about so many tasks, and I couldn't refuse him at all.

"nagging" feels quite appropriate here; it becomes understandable why you wouldn't like him back then.

HNowever we can be going well now, fadays, we get along well. For instance, we both like coffee, and wentgo to coffee-related events together.

The two of us have beenreally grown man.