Many family members who have prayed for the salvation of their loved ones for years, express doubt when their prayers are finally answered. Invariably, they badger the newly saved spiritual neophyte in an attempt to relieve their fears. They notice mistakes and use it as ammunition to prove the experience wasn't "real." Often, they try to make their loved one repeat the prayer of salvation, just to make sure. At best, this discounts the turning point in someone's life. At worst, it causes fear, which stunts future spiritual development.
Here's the thing - your loved one won't understand what happened to him or her. When they accept Jesus, God the Father, Son, and Holy Spirit are a package deal. The Holy Spirit is a new resident in their life and they hardly recognize the voice yet. Old rants and sins may and probably will resurface. The person is saved - not perfect. It make take years for the Holy Spirit to get through on all the issues that need resolution. All who call on the name of the Lord will be saved - trust those words. Be patient. Don't quiz or challenge. Sit back and watch in amazement as your loved one gradually changes.
For an example of what I'm talking about, read He Really Got Saved.