Is it permissible to marry using a fake name and age, while informing the wife of the truth, after changing the personal data of a younger brother to benefit from an older age at work?

There is no harm in marrying with any name—whether it is a kunya (agnomen), a laqab (title), or a name you have adopted—as long as you are known and called by it. This is because the contract is based on the person (the self), not the name. However, if adopting your brother's name and using his documents was a stratagem and deception, you must repent to Allah, unless it was due to necessity. Furthermore, impersonating your maternal brother's name is considered attributing yourself to other than your father, which is forbidden.