According to Chinese records, the Yuezhi Saca were a confederacy of (traditionally) 5 tribes which moved west out of Gansu province of China and eventually settled in Afghanistan where they founded the Kushan empire.
One of the YueChi tribes left in Bactria while the rest of the YueChi invaded india as the Kushans came to rule the Xiyon (Chionites) and were known as KiToLo (Kidara).
The Kidarites themselves were displaced by the expansion of yet another of their families left in Bactria, the YepTal (Hephthal) who came to rule a union of Alchoni and Hua (later known in the west as Avars). In the end, the Hephthalites too eventually invaded India.
Thus according to Chinese sources, the three most prominent conquering dynasties to invade North West India were all of the same original 5 family YueZhi stock.
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