In BalKanda Vishwamitra narrated many stories to Ram n Laxman like birth of ganga, Churning of Aakash Ganga, birth of Kartikeya. He described UMA as daughter of Himalaya. Sati was daughter of Daksha whereas Uma is daughter of Himalaya. Kartikeya was born to Shiva-Parvati(Uma) before the start of Ramayana. The Godesses who tested Ram was Parvati not Sati