There are a number of factors that can play into how close a dog bond is with any one person. In general, though, dogs do seem to form stronger attachments with some people over others. This could be due to things like the amount of time spent together, whether or not there's consistent positive reinforcement involved, and early socialization experiences.
For example, if a puppy spends a lot of time cuddled up with their owner during naps or while watching TV, they're likely to develop a strong attachment to that person. Similarly, if someone is consistently providing treats or taking them on fun walks/runs, the dog is more likely to see them as a favorite. And lastly, if a pup has had lots of exposure to different people and other animals from an early age (before 3 months old), they're more likely to be comfortable around anyone and not as prone to developing separation anxiety.