If it is a civil lawsuit, only the parties and their legal representatives can entrust a lawyer.
In the case of criminal proceedings, the defender:
If a criminal suspect or defendant is in custody, his guardian or near relative may entrust a defender.
Agent ad litem:
The victims of public prosecution cases and their legal representatives or close relatives, and the parties to incidental civil actions and their legal representatives shall have the right to entrust agents ad litem from the date when the case is transferred for examination and prosecution. The private prosecutor and his legal representative in a case of private prosecution, and the parties to an incidental civil action and their legal representatives have the right to entrust an agent ad litem at any time.
In short, relatives must be close relatives, and the scope of close relatives in the criminal procedure law includes husband and wife, parents, children, brothers and sisters. Defenders and agents ad litem here can be lawyers, but they are called by different names. )