Im sorry to tell you but that does not make you a Christian.The fact that "God has no grandchildren" means you aren't a Christian simply because your friends and family are. God only has children-not extended family or relatives!
If you've never asked God personally to forgive you of your sins and come into your heart, then your not a Christian. You may be a good person doing good things, and you may even ready your bible on a regular basis. But being a Christian means you must actually have an actual relationship with the Living King of Kings!
You can be a part of God's family right now! Eternal life with Jesus is a gift. What a great fantastic gift and its free for the asking!
Admit to Jesus that you're a sinner. Tell him you're sorry for trying to run your own life, and ask him to forgive your sins. Pledge that from this very day, your life will no longer be your own. Commit that your life is in his hands to be done with as he wills.
My message for you is to let you know the Glory of God. This happens when you admit to God that you are a sinner and that you have come short of his Glory (as we all have). Once you accept Jesus into your life your life has got to change! When you come to Jesus and ask to enter into his family you life will never be the same. Trust me I know this all to well. The bad things you have done in the past are removed. Your life is renewed. You are now dead to sin and alive in Christ. You are no longer slaves of the devil. You are no long bound up by your sins. I challenge you to read Ephesians 2.
This will explain the wonders of being Alive in Christ and Dead to Sin.
God bless you!