http://revach.net/article.php?id=1245

Section: Halacha   Category: Tshuvos
Rav Moshe Shternbuch: Can A Boy Get Engaged Before His Older Brother?
The Shach (YD 244:13) says that a younger brother must wait for his older brother before getting engaged. It seems that since this is because of kavod and the older brother can be "Mochel". Therefore the younger brother can proceed after getting permission. Rav Moshe Shternbuch (1:739) has two issues with this logic. First, we must question if his mechila is just lip service or if he really means it deep in his heart. Second, it is not only an issue of kavod, it can do real damage to the older brother because people may think there is something wrong with him.

Therefore says Rav Shternbuch we must look at each case to see if the reason for the delayed engagement. If the older brother is extremely picky then there is no embarrassment to him at all. If however he is not particularly fussy but he hasn't been presented with suitable suggestions, then the younger brother should wait a full year before getting engaged and not rely on the mechila of his older brother.

He does make one exception. If the younger brother wants to get married before the age of 20 years old as is the Halacha in the gemara then he needn't wait because everyone will understand the reason why he got engaged before his older brother and it won't cause the older brother's reputation any harm.

Important Note: We try to convey the Tshuva to the best of our ability. We admit that our understanding may not be accurate. Please also understand that this Tshuva may not be the final word on this topic. One should consult a Rav before drawing any conclusions.