dogs don't have a maternal instinct to sit on their pups. conversely, dogs are known to smother their pups to death. there's various theories about that, from reducing the stress on the dog to killing off the runts of the litter.

judging from that reaction of sitting on top of him, i'd suspect that the dog is being teased by this child rather badly and that this needs to be corrected.

http://www.youtube.com/watch?v=bLCoTP2vf44