All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
We did not come across any similar incident that occurred in the time of the Prophet, sallallaahu ‘alayhi wa sallam. The criterion for choosing a wife is her religion and good moral conduct as the Prophet said: “Choose the religious one and you will prosper.” [Al-Bukhari and Muslim]
As regards the age difference, it is not given consideration in the Sharee'ah, as the Prophet, sallallaahu ‘alayhi wa sallam, married Khadeejah who was fifteen years older than him.
If the bride's family told you she was younger than she actually was, then they committed a misdeed and they should repent because this is a kind of lying. If this woman is religious, then it will help you to take the matter less seriously, as Allaah may bless her for your brother and give him children with her who will comfort his eyes.
Finally, we recommend that you have good relations with your in-laws and strive to forget what happened, so that the devil does not take advantage of this and so there will not be any undesirable consequences, such as hatred and enmity. This is the opposite of the religion's objective of harmony and affection in the Muslim society.
Allaah Knows best.