One of the most emotionally devastating things in a person's life is rejection. Rejection by peers, rejection by romantic interests, and, worst of all, rejection by parents. Few things even begin to rival the pain of believing your parents do not want you.
But the great thing is, if you exist, your Heavenly Father has not rejected you. See, life is never an accident. It's not just that you couldn't exist without God's consent, but that He was very actively involved in your creation, and sustains you to this very day. It doesn't matter if you are an unexpected twin/triplet. It doesn't matter if you were an "accidental" result of casual sex, or a one night stand. It doesn't matter if you were initially planned, but regretted. It doesn't even matter if you were conceived by rape. No matter the circumstances of your beginnings, your life matters. You are extremely precious to your Creator, so much so that even though all of us have gone astray and earned His wrath, He actually paid a very high price to get us back.
No matter who you are, or where you came from, just remember: You are not an accident, you are not unwanted, and woe betide the fool who calls you worthless. Though a wretch and a sinner, deserving of wrath, you are unbelievably precious in the sight of the Lord, who loves you so much that He gave His Son, so that if you will only believe in Him, you will be saved. He offers you what no parent ever can.