In choosing the life partner is concerned, preference must be given to religion, then comes beauty, nobility and wealth according to the hadith. If you have found the brother to be of suitable Islamic nature, then go ahead with this without any hesitation. If worse comes and your father and brother are not coming forward in this matter, still you can go ahead with it as according to the Hanafi Madhab, a grown woman can marry without consent.
[Note: Different schools of law have different provisions regarding a woman's right to contract her own marriage independent of a guardian. For more view on this subject browse the keywords marriage: choice of spouse and marriage: contract negotiations.