1) Lois grows up with a brother instead of Lucy.
Sam always wanted a son and never showed a lot of positive attention to Lois. With a boy in his life Lois feels abandoned and is determined to make her mark to prove her father made a mistake by ignoring her. This Lois doesn't care about sports. She didn't make great grades in school because she was in too much trouble, is extremely aggressive in her career, is a perfectionist and regularly walks the borders of vigilantism . Her coworkers would call her "Rabid grizzly Lane" if they weren't afraid of it getting back to her. Despite this, Perry sees potential in Lois and pairs her with Clark. He figures that even though Clark will probably quit, having a partner along might restrain her enough that he won't have to fire Lois.
