Isaac Newton never married. Newton does not appear to have had any romantic relationships as indicated by historical testimony from Newton's letters or his colleagues.
Isaac Newton's relationship with women was marred from a young age when his father died three months prior to Isaac's birth and his mother remarried, sending a young Isaac to live with his grandmother. He was said to have hated his stepfather and refused to see his mother while she was with him.
Newton's temperament was mercurial. He often lashed out at people and repeatedly suffered psychological breakdowns, which seem to have further disconnected him from others. His refuge was his work, to which he devoted himself completely.