तस्मान्नार्हा वयं हन्तुं धार्तराष्ट्रान्स्वबान्धवान्। स्वजनं हि कथं हत्वा सुखिनः स्याम माधव ॥

tasmān nārhā vayaṁ hantuṁ dhārtarāṣhṭrān sa-bāndhavān sva-janaṁ hi kathaṁ hatvā sukhinaḥ syāma mādhava

Therefore we should not kill the sons of Dhritarâshtra, our relatives; for how, killing our kinsmen, may we be happy, O Mâdhava?

In plain words: So Arjuna says they should not kill their cousins. He asks how anyone could be happy after killing their own family. Madhava is a name for Krishna.