The act of self protection gradually becomes an act of care. You can no longer distinguish what is guiding him when he asks for an extra bagel and cream cheese, an extra sticker with a princess or picks out a nice looking stuffed animal from the basement storage even after she is already asleep.
It seems he thinks of her at all times. It's a habit that will hopefully become a second nature.
Witnessing such care leaves me mesmerized and, of course, makes me appreciate my older brother more.