The War of the Spanish Succession  was a European conflict of the early 18th century, triggered by the death of the childless Charles II of Spain in November 1700. His closest heirs were members of the Austrian Habsburg and French Bourbon families; acquisition of an undivided Spanish Empire or Monarchy by either threatened the European balance of power. Charles left his throne to Louis XIV's grandson Philip who was proclaimed King of Spain on 16 November 1700. Disputes over the separation of the Spanish and French crowns, division of territories and commercial rights led to war in 1701 between the Bourbons of France and Spain and the Grand Alliance, whose candidate was Archduke Charles, younger son of Habsburg Emperor Leopold. By 1710, fighting was deadlocked; Allied victories in Italy and the Low Countries had driven the French back to their borders but they could not achieve a decisive breakthrough while Philip was secure in Spain. When Archduke Charles succeeded his brother Joseph I as Emperor in 1711, Britain effectively withdrew, forcing its Allies to make peace and leading to the 1713 Treaty of Utrecht, followed in 1714 with Rastatt and Baden. Philip was confirmed as King of Spain and renounced the French throne; Spain retained the bulk of its pre-war territories outside Europe with their European territories divided between Austria, Britain and Savoy. Longer term impacts included Britain's emergence as the leading maritime and commercial power, the beginning of the decline of the Dutch Republic, the creation of a centralised Spanish state and the acceleration of the break-up of the Holy Roman Empire.
Question: How was Charles related to Joseph I?
Answer: brother