Faasiq (evildoer) leading the prayer
Question

                Sometimes, my brother (blood related)leads me in prayer, when we get together. He is elder than me by 18 years difference. However, he misses a few prayers, due to work, and listen to music. Is it allowable for me to pray behind him. Or do I have the right to request that I should lead, if we want to pray together?
Praise be to Allah.In 
          the case of the obligatory prayer, it is obligatory for you to offer 
          it in the mosque in congregation, if the mosque is nearby. So you should 
          respond to the muezzin when he says “Come to prayer,” and head for the 
          house of Allaah. With regard to praying behind an evildoer, the most 
          correct view is that it is valid to pray behind him even though he appears 
          to be an evildoer. The evidence for that is as follows:  
1 
          – The general applicability of the hadeeth of the Prophet  
          (peace and blessings of Allaah be upon him): “The people should be led 
          in prayer by the one who is most versed in the Book of Allaah…” (Saheeh 
          Muslim, al-Masaajid wa Mawaa’id al-Salaah, 673) 
2 – The Sahaabah (may Allaah be pleased with them) 
          used to pray behind al-Hajjaaj, and al-Hajjaaj was known to be an evildoer.
3 
          – From a logical point of view, everyone whose prayer is valid is acceptable 
          as a imaam to lead the prayers. There is no evidence to suggest differentiating 
          between the validity of a person’s prayer and the validity of a person’s 
          leading the prayer.
al-Sharh 
          al-Mumti’ 
          by Ibn ‘Uthaymeen, 4/307
There 
          is another view: some of the fuqahaa’ say that prayer offered behind 
          an evildoer is not valid, but those who say this do not have any sound 
          evidence to support this view.
No 
          doubt it is better for you to lead the prayer instead of your brother, 
          especially if you meet the conditions for being better qualified to 
          lead the prayer as specified in the hadeeth: “The people should be led 
          in prayer by the one who is most versed in the Book of Allaah. If they 
          are equally versed in the Qur’aan, then by the one who has most knowledge 
          of the Sunnah. If they are equal in knowledge of the Sunnah, then by 
          the one who migrated first …” (Narrated by Muslim). The same applies 
          if you are righteous, for the prayer of the righteous is more perfect, 
          more focused and more in accordance with the Sunnah.
The 
          Standing Committee was asked about a man who was haafiz (i.e., 
          he had memorized the entire Qur’aan) but he did not have a beard, and 
          another who had memorized less Qur’aan but he had a beard. They replied 
          that the one who had a beard, even though he had memorized less Qur’aan, 
          should be given priority over the one who shaved his beard, even though 
          he had memorized the whole Qur’aan. 
See 
          Fataawa al-Lajnah al-Daa’imah, 7/375, and similar fatwas.
 And 
          Allaah knows best.