Can someone please tell me why my brother is doing this?????

I think your little brother's reaction is just through fear. Not saying that's a positive thing, but it's probably the cause. He's afraid but wants to play it cool in front of your older brother. If you have a good and equal relationship with your older brother, why don't you try asking him? Don't mention your little brother, just say you've noticed it and see what his opinion is. Alternatively, try alerting your parents to the situation. They should be able to talk to both of your brothers and sort it out that way while showing them appropriate behaviour. Hope it works out okay!

I would mention it to your parents. Maybe they can help and talk to both brothers on their own about what's appropriate behavior. Other than that I would talk to both brothers and try to see their points on view. Maybe their relationship isn't as bad as it seems but then again maybe it is. From the outside it sounds like your older brother is acting almost like a bully to your younger one. If your younger brother is living in fear of his older sibling beating him up that's not okay. Family is people you should be able to talk to and depend on not people you should be intimated by or be afraid of.

I suggest that you sit and talk to your little brother and tell him he doesn't have to go through this...listen to him, but don't challenge him by asking "Why are you doing this?" That'll make him angry. And don't forget to say that you completely understand the position he is in and you won't bother if he wants that (even if you don't mean it). Hope it helps :)

You need to speak to those who could have some kind of control over the older brother,Your parents.
Dont burden your little brother with what he shoulnt need to deal with unless your parents don't confront the older brother..you may have to then see if you can,or if you have an older relo who can,grand parent,Uncle,a male person might be best.
I wouldnt even tell the older one you are going to tell your parents that your little bro is being treated this way or has been threatend by his brother,because he then will have time to perhaps make something up to cover his story.

Sorry I didnt answer your question,just said what is best to do.
I think quite often bigger sibblings think they are in charge of younger ones,and when they start to see if the younger does what they are told they keep on going,till some one stops them.It may even start from being jelious,if the yuonger get more attention in some way.