“Newton died a virgin”
But I bet that was by choice, and not because no woman would have him. He was a man of rather high position in society, after all.
There’s probably no way to know. He lived during plague years so any contact may have been seen as dangerous. Marriage was almost a business transaction in those days and casual sex outside of marriage would not have been made public. He may have had a fling or two (or more) but there would not have been any record kept.