Jacob and Emma's Love/Hate relationship

I know my children love each other, but they don't always show it. Okay so mostly Emma doesn't show it. I cant blame her, I know her baby brother gets into her stuff, breaks her crayons, sometimes eats her crayons, and takes a lot of lap time away from her. She can't hold him anymore because he struggles and gets away. This was the main reason she liked him in the beginning, because she could hold him and he couldn't leave. She's been asking for a baby sister for awhile now, maybe thinking a girl would work out better. It's escalated since one of her church friends just got a new baby sister and she got to hold her. She wants a baby "just like Gracie" she said to me this morning. I've told her she needs to treat the baby she has better if she wants another one. Not that she is mean to him, but she has very short patience for him, but then again she's only 3 1/2. She must have been listening to me because tonight when Jacob decided he wanted only hugs from his sister and chased her around the house, which Emma usually doesn't enjoy, she gave in. They did nothing but hug and cuddle for about 5 minutes. She even let me take pictures of it, which is another thing she doesn't enjoy. There is nothing that makes me happier, than seeing my children love each other. If she keeps this up, we may give her a baby sister after all.