They don't even have to be your kids to know that feeling. My Brothers and sisters are much younger than me (7, 9, and 13), and I remember when each of them were born. I helped raise them, and you just are intrigued by their overwhelming ability to be such a neat person. I have watched them grow, and it is so amazing that you can love this much, and that I can feel so lit up when i am with them. And try being away from them for any amount of time; you miss them sooo much, and you have this yearning to see them! It's crazy!!