I saw a series of movies a while ago on syfy but I can't really remember much of the plot or the name.?

It was about zombies I think or aliens but I do remember the main male character is an older guy and the main female characterr has a red streak in her hair and is young and in love with the ^ older guy but he tells her shes too young at the end he leaves. Then in the 2nd movie he comes back and shes older and at 1st doesn't recognize him. Then she does and they save the world.