How to find lost family members?

So i wanna help my dad find his lost brother that he never met & i wanna meet him too. Its a really long story... But anyways i went on google & searced people finder & family finder & i get alot of results but mist if the time it saYs that i have to pay. IF ANY ONE HAS FOUND A FAMILY MEMBER OR LOST FRIEND OR KNO OF SOMEONE WHO HAS PLZ TELL ME THE WEBSITE. THANK YOU:)