Abu Hurairah reported,

The Prophet ﷺ said, "No man is to propose marriage where his brother has already proposed, until he either marries her or gives her up."

Bukhari 5144

Sahih

ولا يخطب الرجل على خطبة أخيه حتى ينكح أو يترك

البخاري 5144صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Bukhari
Book
Marriage
Chapter
One should not propose over his brother's proposal until he marries or withdraws
Numbering
Darussalam 5144
Bukhari 5144