Who is the Norse of the god of youth?

It is a Goddess of Youth not a God, she is Idunn or Iduna She lived in Asgard and possessed magical Apples, by eating the gods never grew old.Born of Flowers, like the Welsh Blodeuwedd, Wife of Bragi, God of Poetry - Festivals 3rd and 21st March

Iduna: 'Iduna was the wife of Bragi. She kept golden apples in a box which the gods ate to keep themselves young.'

The Goddess of Youth, she also represents our Earth. Iduna supplied the Norse Gods with the source of immortality, magical apples. There is a metaphysical importance here, for the apple has always been equated with wisdom and how the universe really works. Apples are the sweet fruit of the soil which, when sliced crossways, show a five pointed star, symbolizing humankind made perfect, the age of man, eternal rebirth and much more.

Iðunn is the GODDESS of Youth. She was also custodian of apples which allowed the Æsir (Norse gods) to maintain their eternal youthfulness.

Wife (sometimes listed as "consort") of Bragi, god of poetry.

Its not Allowed even in mythology to say some one god or godess, Instead GOD ALMIGHTY. Obviously its greatest sin. So please stop and don't warm yr grave.