According to Qur'an 'Christians' who really followed Christ are closer to Muslims than the Christians of today?

Why? Polytheism is adding, or associating partners with God, or saying that HE, ta 'ala, has children. Are there any Christians who just believe in one God and not three in one. Any Unitarians left out there? They are the ones whom God says in Qur'an that are closer to Muslims in faith. Where are they?