Yes, MORGANATIC is a Scrabble word!

Letter values in Scrabble US: M 3, O 1, R 1, G 2, A 1, N 1, A 1, T 1, I 1, C 3.

Is it a valid word?

MORGANATIC is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

(of marriages) of a marriage between one of royal or noble birth and one of lower rank; valid but with the understanding that the rank of the inferior remains unchanged and offspring do not succeed to titles or property of the superior

Also: left-handed.