Complex sentence: For the rest of Milutin's reign his youngest son Stefan Constantine was considered as heir to the throne, but in the spring of 1321 Stefan Dečanski returned to Serbia and was pardoned by his father.
Split into simpler sentences: For the rest of Milutin's reign his youngest son Stefan Constantine was considered a heir to the throne. But in spring 1321 Stefan Dečanski returned to Serbia and was pardoned by his father.