I have a hypothesis:
It is located before the events of the first film. The pack from the East tried to invade the one from the West, there was a battle between wolves from the East and the West, Humphrey's parents were Alfas, his duty as Alfas was to protect and hunt, the West pack won the victory of defending his territory, but Humphrey's parents died alongside Salty's, Mooch's and Shakey's parents, protecting their pack, and of course, their puppies. Perhaps Humphrey and hi friends were newborns at that time so they do not mention or remember their parents, or perhaps, they have already overcome that tragic past with their positive and funny attitudes. That why Humphrey is overprotective with his childrens and with Kate for fear of losing them, he is also a skilled improviser who may have taken him out of his parents, saving Kate twice and hi in-laws. That is why Humphrey and his friends take their Omegas work seriously in the first film, even being Humprhey the Omega leader, since they want to avoid at all costs a conflic like the one that ended their parents, perhaps in that event they had not Omegas (Since no old Omega is observed, they are all young or Humphrey's age) and if there were, perhaps they were inexperienced, lazy or they could have died defending their pack.
What do you think about this? :D