My dad was addicted to alcohol before we were born and I want to know how this affected me and my sister
This a great question and there’s no straightforward answer. If the gene for alcoholism is in your family tree, there is a good chance (but not guaranteed) that this gene could be passed to your children. However, having this gene does not mean that your child will become an alcoholic.
I recommend reading more about the Foetal alcohol syndrome: https://www.nofasd.org.au/alcohol-and-pregnancy/what-is-fasd/