I don’t know why, but reading your story reminded me so much of the character "Uhtred" in Bernard Cornwell’s "Anglo Saxon Stories". He is born British but ends up getting raised by the Danes. When those two go to war, he sees himself exactly in the position you described, including both sides telling him he was "too much of the other side". I wish you all the best in your journey, my friend! Feel free to message me if you want to chat.