Thanks To My Dead Unborn Siblings, I Am An Only Child!

I was born and than two years later, my sibling was suppose to be born but because of it health. The child died. Than one year later, my other sibling was suppose to be born but because of it health. The other child too died. Now after growing up as a only child with the pros and cons, I worry about my future. When my parents die, I will be alone. Yes hopefully I will have a husband by the time my parents die and maybe with one or two kids, but still I will be the one to have the responablities of taking care of my parents. That makes me sad and worried all at the same time. Please help me! Please!