The relation of Jupiter to Janus is problematic. Varro defines Jupiter as the god who has potestas (power) over the forces by which anything happens in the world. Janus, however, has the privilege of being invoked first in rites, since in his power are the beginnings of things (prima), the appearance of Jupiter included.G. Dumézil ARR above p. 101 and 290. Discussed at length by Augustine, City of God VII 9 and 10. Also Ovid Fasti I 126.
