Editing Alfonso X of Castile (section)

===Early life===
Alfonso was born on 23 November 1221{{sfn|Thacker|Escobar|2002|p=20}} in Toledo, Kingdom of Castile.  He was the eldest son of [[Ferdinand III of Castile|Ferdinand&nbsp;III]] and [[Elisabeth of Swabia|Elizabeth (Beatrice) of Swabia]].{{sfn|O'Callaghan|1998|p=46}} His mother was the paternal cousin of [[Frederick II, Holy Roman Emperor|Holy Roman Emperor Frederick&nbsp;II]], to whom Alfonso is often compared. His maternal grandparents were [[Philip of Swabia]] and [[Irene Angelina]]. Little is known about his upbringing, but he was most likely raised in Toledo. For the first nine years of his life Alfonso was only heir to Castile until his paternal grandfather king [[Alfonso&nbsp;IX of León]] died and his father united the kingdoms of Castile and [[Kingdom of León|León]]. He began his career as a soldier, under the command of his father, when he was sixteen years old.

After the accession of King [[Theobald I of Navarre]], Ferdinand tried to arrange a marriage for Alfonso with Theobald's daughter, [[Blanche of Navarre, Duchess of Brittany|Blanche]], but the move was unsuccessful. At the same time, he had a romantic relationship with [[Mayor Guillén de Guzmán]], who bore him a daughter, [[Beatrice of Castile (1242–1303)|Beatrice]].  In 1240, he married Mayor Guillén de Guzmán, but the marriage was later annulled and their issue declared illegitimate. During the 1240s, alongside his father, he conquered several Muslim strongholds in [[Al-Andalus]], including [[Conquest of Murcia in 1243|Murcia]], [[Alicante]] and [[Cádiz]].

In 1249, Alfonso married [[Violant of Aragon|Violant]], the daughter of King [[James I of Aragon]] and [[Violant of Hungary]],{{sfn|Previté-Orton|1952|p=902}} although betrothed already in 1246.