A brief history of this first Deity form, Lord Rangantha!
యో బ్రహ్మాణం విదధాతి పూర్వం యో వై వెదాశ్చ ప్రహినోతి తస్మై…
Yo bramhaanam vidadhati poorvam yo vai vedaascha prahinoti tasmai
God gave birth to the four headed Brahma (through a lotus that emerged from His navel). He gave Brahma a manual named Vedas and asked him to create; Bramha refused to take this task because he could neither take his eyes off from God nor his heart away from God.
God then offered a Deity that resembled Him exactly in both form and qualities, but in a smaller frame to keep with him. Brahma then agreed and began the creation. Amongst many families, Ikshwaku is also a family that Brahma created. Upon the request of Ikshwaku, Brahma offered the Deity of Ranganatha to him.