Complex sentence: He set her aside because "she was not pleasing to him", and when he formed a political alliance with Sancho I of Pamplona, he was married to that king's daughter, Sancha.
Split into simpler sentences: He set her aside because "she was not pleasing to him". And when he formed a political alliance with Sancho I of Pamplona, he was married to that king's daughter, Sancha.