As she came to him under the influence of desire, the son of Pritha accepted her as his wife. Thus it was that Arjuna's son was begotten upon another's wife.
भार्यार्थं तां च जग्राह पार्थः कामवशानुगाम्। एवमेष समुत्पन्नः परपक्षेऽर्जुनात्मजः॥