http://www.peoplefinders.com/?CMP=Google&utm_source=google&utm_medium=cpc&utm_term=lost%2Brelative&utm_campaign=pf%2bmain&mt=b
http://www.peoplesearching.com/people-searches/family-member-search.php?keyword=family%20finding&source=google
http://boards.ancestry.com/localities.britisles.ireland.cmcproject/503.2.1/mb.ashx
there are tons of sites that offer this kind of service.....and no its not free even tho some claim to be......but it is a lot cheaper than hiring a private investigator.......
also the probate judge office in ur area can help u in some cases especially if there was no will........
other than that all i can say is go thro his phone and or phone bill and see if he called or had his family's phone numbers........also he may have had a "little black book" with his family's contact info in it someware........good luck
also if he has had a cell phone or house phone for a wile i would suggest keeping the service on since some 1 who knows his family may call it.....