Countess Sophie of Hainaut was married to Count William II of Hainaut, a prominent nobleman in the 13th century. Their union was significant in strengthening political alliances in the region. William was known for his leadership and played a crucial role in the governance of Hainaut. Together, they had several children, including Countess Margaret of Hainaut, who later became an influential figure in her own right. The marriage between Sophie and William helped to solidify the power of the House of Hainaut during a time of political turbulence in medieval Europe.