You never saw such a fight! When the snow-daughter saw that her fire-brother had killed the king in his blazing embrace, she flew at him in a cold fury. He turned into a fire-ball and exploded with passion and rage.
They had both been so alone and pent-up—she in her frozen underground palace, and he in his furnace. No one could get close to either of them. The king tried to live with them both, but in the end, they all succumbed.
A Guest at the Fiery Feast in The Snow-daughter and the Fire-son, Yellow Fairy Book