Assuming that your brother is 22 year old, You should provide an explanation letter in this regard.
Dear IRCC Officer,
This is to explain that my younger brother's current passport has an error, it has a wrong middle name. My younger brother's age is ___ and he will be part of my parents immigration application as a dependent. A copy of current passport (with wrong middle name is provided). The current passport number is ________ ; The middle name in the current passport is ___________ but based on the birth certificate the correct middle name on passport should be __________
We have started the process of getting a new passport with correct middle name, in Philippines i could take up-to 6 months to get a new passport with correction. Meanwhile, In order to meet the PGP application deadline we are providing the current copy of passport. As soon as we have the renewed passport, we will provide IRCC office a copy of the new passport.
Meanwhile, kindly accept the application package for my parents immigration with the current passport of my younger brother. My brother's full name is ____________