Ideally, socializing puppies should start the day they're born, handling them every day thereafter so they get accustomed to the human scent and the human touch to every part of their body. When this doesn't happen or only happens sporatically, puppies become leary when humans later try to interact with them.
(This is why many puppy mill puppies, from mass produced breeders who don't have the time to properly socialize, are shy and sometimes to the point of being fear aggressive.)
My suggestion with your husband and son (but only one at a time so it won't be overwhelming) is to sit on floor in middle of room so their size won't be as intimidating, play with the pup's toys, gently tossing them about, retrieving them, to show the puppy what a good time they're having. They should not make any moves in trying to catch or touch the puppy, but instead let the puppy watch from a distance and build up trust on its own terms. Puppies are naturally curious and will observe how much fun they're having and will (eventually) want to join in too, just like it would with its litter mates. Treats should be available so once the puppy approaches, it can be rewarded.
Once the pup is approaching on its own, getting its treat, then go to the next step,
which is....
Touching the flank area of the puppy (something I learned from being a puppy raiser for several well-known poodle breeders). Gently touching the flank area is a familiar touch to them, going back to the moment they're born when mama nudges them up to her teets.
Just like any behavior modification, take baby steps to build confidence instead of looking for an immediate "fix".
Chirp & the ChirpnTails (animal performers)
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