Simplify the following text for a Grade 3 native English-speaking person.
Original: Robert II ( 2 March 1316 â `` 19 April 1390 ) became King of Scots in 1371 as the first monarch of the House of Stewart .
Simplified: Robert II ( early 1316 - 19 April 1390 ) was King of Scotland from 1371 through 1390 . He was the first king of the House of Stewart .