One issue here is the expectation people respond. You are not owed action in response to your 'requests' For instance your brother, while possibly rude, doesn't owe you a response. Consider too he may have a valid reason not to reply. My own doesn't.

I want to point out you are self aware that you might have such a problem, this is huge for it means you wish to change.

If you haven't done so already, observe the actions and behavior of those around you particularly on social media. Perhaps you might emulate them.

You have already begun the process - that of giving this issue consideration. I agree with those above who suggest this may be a result of the need for attention, self worth, and validation. So consider those things in your life both now and in the past that have caused you to feel these things are missing in your life. My CBT therapist had me write down a long 'credo' namely a statement of why I have long felt I have not been deserving of those things that made me feel that way and why I am deserving of them. My self worth increased several times - enough that I stopped my own behavior to seek validation from others.