Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- Muslims should abide by the laws of the land in matters related to the age of marriage.
2- The age difference between boys and girls cannot be a deterrent as long as they fulfill the conditions of valid marriage.
In responding to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
You should abide by the laws of the land in such matters. It is my understanding that many countries, including Canada, do not allow marriage under the age of eighteen. If you are sixteen and want to get married, you can do so in some provinces with your parents’ consent.
Islam teaches to abide by the laws of the land, for such rules are intended to safeguard the parties’ interests.
The age difference between boys and girls cannot be a deterrent as long as they fulfill the above requirements. Remember, Prophet Muhammad (peace be upon him) was 25 when he married Lady Khadijah (may Allah be pleased with her), who was forty. So the age differences should not be a reason to prevent marriage.
Almighty Allah knows best.