Vasilia Link

With the development in the field of science and technology, mankind finally began to make headway in interstellar explorations, a project which had been frozen for over a century due to insufficient technology.
But with discovery came danger. When an exploration unit suddenly stumbled upon an inhabitable land, they inadvertently alerted the denizens living there, leading to mankind's first intergalactic war. Casualties numbered in millions in both species, where the humans finally made a drastic decision to introduce the first ever battle mechas -Valkyries into the battlefield.
Valisia Link: a psychic connection between two individuals with syncing brainwaves. This is normally common between siblings or twins, but it could also happen between two complete strangers. Usually the Vasilia Link can only be formed between siblings, or individuals with opposite genders.
Valisia Link is said to be the psychic manifestation of the Yin and Yang, where Yin manifests in the female counterpart and Yang manifests in the male counterpart. Together, they form the Vasilia Link, which aids in their control of the battlemechas.
The earlier the link manifests the stronger the connection as they grow up. With the whole of humanity pouring in their various resources, they finally gathered children from all over the vast territory of Galaxia, Humanity's new homebase, and opened an Academy that focused solely in training these children to become the next generation of mecha-warriors, with the power to wiled the Vasilia Link.