The two sons who took birth from the womb of Marutvatī were Marutvān and Jayanta. Jayanta, who is an expansion of Lord Vāsudeva, is known as Upendra.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
मरुत्वांश्च जयन्तश्च मरुत्वत्यां बभूवतुः । जयन्तो वासुदेवांश उपेन्द्र इति यं विदुः
marutvāṃśca jayantaśca marutvatyāṃ babhūvatuḥ | jayanto vāsudevāṃśa upendra iti yaṃ viduḥ
SB 6.6.8