http://revach.net/tefila/article.php?id=3418

Section: Halacha   Category: Tshuvos
Shevet HaKehosi: Standing Up For Your Big Brother
TheShulchan Aruch (YD 240:22) paskens that you are obligated to honor yourbig brother (Achiv HaGadol).  Does that include standing up for himwhen he walks into the room? 

The Shevet HaKehosi discussesthis issue in 1:262.  He says that the Bais Meir points out that whenit comes to a big brother you are only obligated to give him kavod, butthere is no chiyuv of Morah, to fear him.  The Sefer Chareidim holdsthat standing up for someone falls under the category of kavod, and soit seems also from the Shulchan Aruch.  On the other hand the ShaarEphraim and the Makneh both hold that standing up is a matter of morahand not kavod, so you might not be obligated.  However, the Brisker Rovin Chidushei HaGriz (Hilchos Talmud Torah) holds that you are chayav inboth kavod and morah of your big brother. 

Since many poskimhold that the obligation of honoring your big brother is Min HaTorah,the Shevet HaKehosi says you should be machmir and stand up for himsince it is a Safek D'Oiraisa.

It should be noted that GilyonMaharsha and Bais Lechem Yehuda bring from other sources that thisobligation is not for any brother that is older than you, only theoldest of the brothers.  It seems clear that the obligation includeseven a brother who is not the oldest in the house and is preceded bysisters.

Important Note: We try to convey the Tshuva to the best of ourability. We admit that our understanding may not be accurate. One should learn the tshuva to verify the accuracy of our interpretation.  Pleasealso understand that this Tshuva may not be the final word on thistopic. One should consult a Rav before drawing any conclusions.