In Hollywood movies, parents and their children don't look alike. They can even have different hair color. First I thought producers were just lazy. Now I know that it's because for Jews is not uncommon to cheat and not know who the biological father is. Many Jewish families have children who don't look like their legal father.
Not that bad. Common for white families. I have blonde hair, my mother has red hair, my father has black hair. I get blonde hair from my paternal grandfather, my dad has black hair from his paternal grandfather.
But even if this is a jewish thing, which I don't exactly doubt, I don't think it's something that would change a whole lot if there were 0 jews in Hollywood at all. It's just not very likely that you will have a child actor/actress who just happens to look just like the adult actor/actress.