Simplify the following text for a Grade 10 native English-speaking person.
Original: Alexander III ( Mediaeval Gaelic : Alaxandair mac Alaxandair ; Modern Gaelic : Alasdair mac Alasdair ) , King of Scots , was born at Roxburgh on 4 September 1241 and died on 19 March , 1286 .
Simplified: Alexander III ( Medieval Gaelic : Alaxandair mac Alaxandair ; Modern Gaelic : Alasdair mac Alasdair ) ( â `` ) was King of Scots from 1249 to his death .