Newton's early life was marked by the absence of his father and the separation from his mother when she remarried. This abandonment likely had a profound impact on his emotional development and may have contributed to his later tendencies toward solitude and intellectual pursuits.

During his time at the King's School in Grantham, Newton lodged with the apothecary William Clarke. It is suggested that he may have had a romantic interest in Clarke's stepdaughter, Katherine Storer. This remains the only known potential romantic involvement in Newton's life, though whether the feelings were reciprocated is unknown. While Newton had a good relationship with the Storer family, he ultimately never married.

Throughout his adult life, Newton remained unmarried and largely devoted to his work. He maintained a few close friendships, most notably with Nicolas Fatio de Duillier, although this relationship eventually soured. He was known to be fiercely protective of his intellectual property and quick to defend his ideas against criticism, which sometimes led to strained relationships with other scientists.

In his later years in London, Newton was closely cared for by his niece, Catherine Conduitt, and her husband, John Conduitt. Catherine served as his hostess and confidante, providing companionship and managing his household. This relationship provided him with a degree of comfort and social connection in his later years.

Overall, Isaac Newton is viewed as a solitary figure, deeply absorbed in his intellectual pursuits. While he interacted with other scientists and had some close relationships, he was not known for having a wide circle of friends or a particularly active social life. His dedication to science seemed to take precedence over personal relationships.