As far as I know, different lawyers in the same law firm can act as defenders of different criminal suspects in the same case. See Provisions on Several Issues Concerning the Implementation of the Criminal Procedure Law. "Defenders shall not defend more than two criminal suspects and defendants in the same case, nor shall they defend more than two criminal suspects and defendants who have not been dealt with in the same case but are related to their crimes."
Legal objectivity:
Article 33 of the Criminal Procedure Law of People's Republic of China (PRC) * * * A criminal suspect or defendant may entrust one or two persons as defenders in addition to exercising the right of defense by himself. The following persons may be entrusted as defenders: (1) lawyers; (2) A person recommended by a people's organization or the unit to which the criminal suspect or defendant belongs; (3) Guardians, relatives and friends of criminal suspects and defendants. A person who has been sentenced to punishment according to law or deprived of or restricted personal freedom shall not act as a defender. A person who has been dismissed from public office or has his lawyer's or notary's practice certificate revoked may not act as a defender, except the guardian or near relative of the criminal suspect or defendant.