You're half right. The tale of Turin Turambar is based on one part of The Kalevala (which is the national epic of Finland). In Kalevala there is a story about Kullervo, who's fate is in many ways similar to that of Turin Turambar.
It's a story about this boy, Kullervo, who has lost his family. Kullervo is believed to be an orphan and the sole survivor of a clan who were completely slaughtered. As he grows up he cannot find his place in life and experiences one misfortune after another. In the end he finds his sister, but he doesn't recognise her and so he marries her. Eventually Kullervo discovers the truth and commits suicide by falling on his own sword, like Turin did.
Here's a site that tells a bit of the the similarities between Kalevala and Silmarillion:
http://www.scandga.org/Insights/Wint...02/Tolkien.htm
[ September 22, 2002: Message edited by: Kalevala ]