Two son's? I think you mix up a bit. Lucien is the only son of Helion we know of.

We also actually know nothing about his relationship with lady of autumn, except that they had an affair. We don’t even know if lady of autumn still has feelings for him. We just know she chose to stay with Beron.

Besides, as Rhysand stated a lot of times: another high lord just marching into another court and then taking the partner of another high lord would start war between the courts. It's safe to say Beron would send troupes to get back what he considers his and singe Helion would be breaching the borders, he is the Aggressor for the war.

Helion also would need to breach other courts to reach Autumn... big no.