He loves you, you're pack-mates. He's bonding with you and playing and treating you as he would littermates, a parent, or even an "uncle" or "aunt."
One question, though: What kind of dog is he? You may have some dominance "feelers" being put out. Make sure you groom him a little before he's allowed to groom you, by scratching him, doing things like checking his feet, ears, teeth, etc., and then again after he's groomed you. That helps to set you up as the dominant "dog." Brushing him is a good way to end the session. It also sets up good habits for later on, when he may not want to be still when you want - or need - to clean him up.
Just remember, dogs don't typically groom anyone they don't love and consider "family." Just try not to yelp too loud when he accidentally pinches! (g)