For other persons with the same name, see Amyntas
Amyntas (Greek: Ἀμύντας), son of Alexander from Mieza and brother of Macedonian general Peucestas, was appointed somatophylax of Philip III Arrhidaeus at Triparadisus in 320 BC. This appointment suggests that Antipater trusted Peucestas more than he did Peithon.
References
Amyntas of Mieza Wikipedia(Text) CC BY-SA