Younger brother getting married before older brother
Question

                I am a young man aged 21 years. I want to get married but I have two older brothers who have not got married yet. Is it permissible for me to get married before them?
Praise be to Allah.This question was put to 
          Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him), who said:  
          
I say to the brother who 
          is asking the question, you are not too young to get married. ‘Amr ibn 
          al-‘Aas got married when he was 11 years old, and he had a child. Hence 
          it was said that that there was only thirteen years between him and 
          his son ‘Abd-Allaah.  
I say to the brother who 
          is asking the question, put your trust in Allaah and get married, and 
          when it is easy for your two older brothers to get married they will 
          get married too.  
This is one of the grievous 
          mistakes that some people make, when they do not let the younger daughter 
          marry so longer as there is an older sibling. This is a shame.  
          
If someone whose character and religious 
          commitment are suitable proposes marriage to her, then they should let 
          her get married to him. Maybe there is something preventing the older 
          sister from getting married. Often what happens is that it is decreed 
          that the younger sister will marry first, so if the younger sister is 
          not allowed to marry first, the older sister is prevented from marrying. 
          Then when the younger sister gets married, Allaah opens the door for 
          the older sister (to get married). This is something which is well known 
          from experience, i.e., that not letting one daughter get married may 
          prevent another from getting married. The same may apply to having children. 
          We have heard more than one story of a man who gets married and remains 
          childless for fifteen years, then he takes a second wife and the second 
          wife gets pregnant from the first night of marriage, and then the first 
          wife get pregnant at the same time.  
So we say to the one who 
          is asking: get married and do not think that this means you are disobeying 
          your parents or severing your ties of kinship with your brothers.