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.