All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
If the suitor is religious and well-mannered, then his proposal for marriage should be accepted, since the Prophet, sallallaahu ‘alayhi wa sallam, said: "Whenever you receive a proposal for marriage from a man whose religion and manners please you, then accept him. For if you do not do so, temptation and great mischief will fill the earth." [Ibn Maajah and At-Tirmithi]
The fact that his brothers commit certain sins is not a valid reason to refuse his proposal since he cannot be held accountable for the deeds of his brothers. Allaah The Exalted Says (what means): {“And no bearer of burdens will bear the burden of another.”} [Quran 6:164]
Furthermore, the fact that he has his own separate residence makes him far from their bad influence. We beseech Allaah The Almighty to guide you to attain what He loves and what pleases Him.
Allaah Knows best.