You cannot see a soulmate relationship in a chart. No aspects in the world can show you that. It's something that goes beyond astrology and our understanding of it.
You might have the best possible aspects in synastry or composite, but it still might not work out.
You also might have the worst possible synastry/composite and still be together till your old ages.
So no, astrology cannot define a soulmate.
If you want to know if he is fated, look more at asteroids, not so much synastry. Look at the more spiritual side of astrology. Davision chart cannot help with that. Nor can a composite. Look for touches to the vertex, juno, part of fortune, sun/moon midpoint, amor, valentine, psyche, eros and the general love asteroids.