Aragorn is the son of Arathorn and the heir of Isildur and Elendil.
After the early death of his father Arathorn,his mother Gilraen moved with him to Rivendell where Aragorn was educated by Elrond.When he was twenty years old Elrond told Aragorn that he comes from a royal family.Some years later, Aragorn fell in love with Elrond's daughter Arwen.Elrond promised Aragorn that he could marry his daughter as soon as he would be king of Arnor and Gondor.
Aragorn didn't speak of the fact that he was a king, most of the people just knew him as 'Strider'. He is the leader of Dunedain and most of the time he travels alone through middle earth.Many people distrust him because a ranger could be everything a vagabond or a mugger.When Gandalf tells him that the one ring has been found,Aragorn starts to search for Gollum and finally , he joins the Fellowship of the Ring.After Gandalf fell into shadow of Moria Aragorn leads on the Fellowship.