Regarding it being disliked for a person to propose after his brother's proposal
باب فِي كَرَاهِيَةِ أَنْ يَخْطُبَ الرَّجُلُ عَلَى خِطْبَةِ أَخِيهِ
Sunan Abu Dawood, Book of Marriage (Kitab Al-Nikah)(view book)
Abu Hurairah reported the Apostle of Allah ﷺ as saying “ A man should not seek the hand of a woman in marriage when his brother has already sought her hand.”
حَدَّثَنَا أَحْمَدُ بْنُ عَمْرِو بْنِ السَّرْحِ، حَدَّثَنَا سُفْيَانُ، عَنِ الزُّهْرِيِّ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ ﷺ " لاَ يَخْطُبُ الرَّجُلُ عَلَى خِطْبَةِ أَخِيهِ " .
Classification
Narrated Abdullah ibn Umar:
The Prophet ﷺ said: One of you must not ask a woman in marriage when his brother has done so already, and one of you must not sell (his own goods) when his brother has already sold (his goods) except with his permission.
حَدَّثَنَا الْحَسَنُ بْنُ عَلِيٍّ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ نُمَيْرٍ، عَنْ عُبَيْدِ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ ﷺ " لاَ يَخْطُبُ أَحَدُكُمْ عَلَى خِطْبَةِ أَخِيهِ وَلاَ يَبِيعُ عَلَى بَيْعِ أَخِيهِ إِلاَّ بِإِذْنِهِ " .