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.
It is permissible for you to take the charge offered by your brother in return for settling his needs. You are blameless as it is included in the permissible charge under Sharee‘ah. Allaah The Almighty Says (what means): {And whoever comes up with it shall have a camel's load; and for that I am a sure guarantor.} [Quran 12: 72]
However, it is conditioned that the mentioned charge should not be in return for work that you or other employees are responsible to do by virtue of your job; in this case, the offered charge is considered bribery.
Allaah Knows best.