Valdemar Christian of Schleswig-Holstein

Valdemar Christian of Schleswig-Holstein (1622–February 26, 1656) was the son of king Christian IV of Denmark and his morganatic spouse Kirsten Munk. He had the title Count of Schleswig-Holstein.

In 1643, he was sent to Russia to marry Irene of Russia, the daughter of Tsar Michael of Russia, but as he refused to convert to the Orthodox faith, he was kept prisoner until 1645. In 1648, he came into conflict with his half-brother Frederik III of Denmark because of his wish to be elected king instead of Frederick, and after this, he lived abroad. He served in the Swedish army from 1655 and was killed in Poland in 1656.

...
Wikipedia