This weekend, my wife and I headed out for a long awaited "date night". My son knew something was up immediately, and began to show his displeasure minutes after the baby sitter showed up. He was fine just after we left (yes, we text back and forth with the sitter), but just before departure, I paid attention to my daughter. While the boy was crying, she disappeared into his room, and came out with a favorite stuffed animal. She began coaxing him with a soft and upbeat voice, trying to hand him his stuffed buddy. We mentioned to her the need to help, but I left knowing that she does those things by instinct theses days.
Sure, there are plenty of "mine", "don't touch", and "daaaaaddddyyyy" moments to fill a toy box. However, she wants to push him in his stroller, feed him treats, quiet his crying and so forth. I fully believe that as she welcomed a little brother, WE tried to make the transition easier. We have special times with her alone, I still read books to her before bed, and other things that make her feel special and loved on an individual basis, as well as a sibling. I know that's helped, and will continue to do so.
I've found some additional articles on Kids Health, Family Circle, and Parenting. The address sibling rivalry/harmony and overall getting along. I hope we can keep on this path. It'll be a fun ride.