There is nothing specific you can ask Allah for your brother. You should generally ask Allah to guide him and Allah will answer your prayers.

What is the best way I can ask Allah to guide my brother, make him obedient and respectful towards elders, have love for religion, have good manners, become a very good Muslim?

Supplications | March 20, 2014 7:06 pm
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Is there any prayer or dua for becoming pregnant?
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When we recite the morning and evening adhkar do we have to raise our hands as we are making duah? Should they be recited immediately after Fajr and Maghrib, or can they be delayed?