Shulchan Aruch (Y.D. 240 : 22) A younger brother is Mechuyav to
honor his older brother.*
When does this same chiyuv require the older brother to honor his younger brother?
*The Poskim add, even if the younger brother is a bigger Talmid Chacham
If twins were born in a leap year one on the 29th day in Adar 1 (Rishon)
and the second one was born on the 1st. of Adar2 (Sheini),
The Hilchos Ketanos (2 :174) writes," being the younger brother
becomes a Gadol before his older brother*, the older brother is
Mechuyav to honour his younger brother".
The Shevus Yackov argues and holds even in this case the younger
brother, is Mechuyav to honour his older brother.
Fromhe Ramban ( Breishis 32:5) it seems
that Yackov wasn't required to honour Esau
because he sold him the Bechora . Could be
that Esau would be mechuyav to Honour Yackov.
*If Bar Mitzvah falls in a regular year