The best thing about watching them together is seeing how well they understand each other. I hardly see a parent get down on the same level as the child and really play with them. He can entertain Sebastian for hours playing, not just with toys, but chasing games, hide and seek games, random games that don't even have a name. It's like Brian not only remembers being a kid, he can put himself right back there in that moment and actually be a little boy, all the while being a parent and making sure Sebastian is learning something and not breaking anything (mostly). He let's him have fun and never dampens his excitement, something that I have a hard time doing when the excitement is so great he's screaming with glee at a new record decibel. He has more patience then most people I know combined, and can really let Sebastian do things on his own.
I know there are other stay-at-home dad's out there in the world, but I don't personally know any. That makes Brian quite unique as a man, he's willing to do something most men are not- put himself in a "woman's role" so to speak. Honestly how many guys do you know that are willing to even try that? Of course there are many factors that go into this decision, and this sparks a whole debate that is worthy of another post entirely, so I'll save that for later. ;-)