Sayyiduna Abu Hurayrah (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) forbade "that a man should raise the price over the offer of his brother, and that he should send a marriage proposal over the proposal of his brother."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10895