I agree, some Christians don't know. However, many must know. For example, there are a many Christians living in and around Jewish communities. Those who know would likely not want others to know.

David and Jonathan: yes. Within religion we are programed to see only one view. I once asked a home church leader about David. He was known as "a man after God's own heart", esteemed, beloved, revered and a hero of Christianity -yet he had a palace full of concubines and had several wives. I was told: "shh, we don't talk about that".