The Messenger of Allah said: "A man is not to sell over his brother's sale, nor is he to propose to whom his brother has proposed."
النَّبِيَّ ﷺ وَقَالَ أَحْمَدُ قَالَ رَسُولُ اللَّهِ ﷺ لاَ يَبِيعُ الرَّجُلُ عَلَى بَيْعِ أَخِيهِ وَلاَ يَخْطُبُ عَلَى خِطْبَةِ أَخِيهِ قَالَ وَفِي الْبَابِ عَنْ سَمُرَةَ وَابْنِ عُمَرَ
A person should not enter into a transaction when his brother (had already entered into but not finalised), and he should not make proposal of marriage upon the proposal already made by his brother, until he permits it.
عَنِ النَّبِيِّ ﷺ قَالَ لاَ يَبِعِ الرَّجُلُ عَلَى بَيْعِ أَخِيهِ وَلاَ يَخْطُبْ عَلَى خِطْبَةِ أَخِيهِ إِلاَّ أَنْ يَأْذَنَ لَهُ
A person should not enter into a transaction when his brother is already making a transaction and he should not make a proposal of marriage when his brother has already made a proposal except when he gives permission.
عَنِ النَّبِيِّ ﷺ قَالَ لاَ يَبِعِ الرَّجُلُ عَلَى بَيْعِ أَخِيهِ وَلاَ يَخْطُبْ عَلَى خِطْبَةِ أَخِيهِ إِلاَّ أَنْ يَأْذَنَ لَهُ
A man must not make proposal of marriage to a woman when his brother has done so already. And he must not offer a price for a thing for which his brother had already offered a price; and a woman must not be combined in marriage with her father's sister, nor with her mother's sister, and a woman must not ask to have her sister divorced in order to deprive her of what belongs to her, but she must marry, because she will have what Allah has decreed for her. (Using translation from Muslim 1408g)
عَنِ النَّبِيِّ ﷺ قَالَ لَا يَسُومُ الرَّجُلُ عَلَىسَوْمِ أَخِيهِ وَلَا يَخْطُبْ عَلَى خِطْبَةِ أَخِيهِ
[Machine] The Prophet ﷺ said, "A man should not sell on the sale of his brother, nor propose to marry the betrothed of his brother, except with his permission. And perhaps he will give him permission."
عَنِ النَّبِيِّ ﷺ قَالَ لَا يَبِيعُ الرَّجُلُ عَلَى بَيْعِ أَخِيهِ وَلَا يَخْطُبُ عَلَى خِطْبَةِ أَخِيهِ إِلَّا بِإِذْنِهِ وَرُبَّمَا قَالَ يَأْذَنَ لَهُ
Abu Hurairah reported the Apostle of Allaah ﷺ as saying “ A man should not seek the hand of a woman in marriage when his brother has already sought her hand.” (Using translation from Abū Dāʾūd 2080)
قَالَ رَسُولُ اللهِ ﷺ لَا يَسْتَامُ الرَّجُلُ عَلَى سَوْمِ أَخِيهِ وَلَا يَخْطُبْ عَلَى خِطْبَةِ أَخِيهِ
"لا يَبِيع الرَّجُلُ عَلَى بَيعِ أَخِيهِ، وَلا يَخْطُب عَلَى خِطْبَةِ أَخيهِ إِلا أَنْ يَأذَنَ لَهُ".