One thing is to belong to a true religion and another thing is to encourage them or give them reasons to join your religion, if you do not belong to a true religion you will be seen as an agent of Satan.
Be convincing your loved one is by one living an example life, when you say you belong to a true religion. It should reflect in your actions, in your conversation with people. A saying goes this way Acton speaks louder than voice meaning your avtion goes first before your voice.
Another is let them know that you have realise the truth and love that on belonging to a religion, then extend the love to your loved ones. Share the love you have reclaim with them.
Let the know that serving God comes with good things and share the good things with them, to the faith , backing it up with the word of God.
In Corinthians 9 vs 20-22 where Apostle Paul did well by convincing them to belong to Jesus Christ and also convert them to belong to Jesus Christ because he understands that in Jesus Christ comes the best religion and in Him we have peace, longlife and enjoy His abundance.