Siblings

Tonight my mother in law sent me a text telling me that Piper asked her if she loved her. Where does a child who is not yet 3 come up with this? How does she even know what that means? I feel that I have been neglecting her lately and I don't mean to. I see the jealousy in her eyes whenever Brylin gets attention, which is most of the time. Unfortunately, a 10 month old can't do a lot for herself yet. Piper is in the full swing of being in the terrible 2's and they are bad. Everyday it seems I am yelling at her more and more, yet the yelling does not make her behave any better. I know I need to try something else, but what? I was raised with fear. I was too scared to upset my father. He was not abusive, but his temper is something I would rather not see. I don't want my girls to fear me, however, how do you reason with a toddler? They are too young to reason. Maybe I am under estimating her ability. She has surprised me in almost all areas when it comes to what she has learned and can do. How do I make sure she knows she is loved? How do I make her understand that Brylin is not more important than she is just because right now she gets more of the attention?