I recently was reading on Wikipedia :
Kartikeya is an ancient god, traceable to the Vedic era. Archaeological evidence from 1st-century CE and earlier, where he is found with Hindu god Agni (fire), suggest that he was a significant deity in early Hinduism. He is found in many medieval temples all over India, such as at the Ellora Caves and Elephanta Caves.
I also read about
रुद्रो रुद्रश्च दन्तिश्च नन्दिः षण्मुख एव च । गरुडो ब्रह्मा विष्णुश्च नारसिहंस्तथैव च ।।
rudro rudrascha dantischa nandi sanmukha eva cha | garudo brahma vishnuscha narsimhastathaiva cha || [Yajurveda Taitteriya Aranyaka 10.1.15]
The names of God mentioned are: Rudra, Danti, Nandi, Shanmukha, Garuda, Brahma, Vishnu, Narsimha
Where Shanmukh or six faced, should be a name of Kumara Itself. What and where are the historical origin of the cult of Lord Kartikeya ,other than the Yajurveda mentioned here, especially connected to Lord Shiva's Family?