His parents never thought he would have much of a life when he was born. He was the 4th son in the family...and only a 3rd cousin to the leadership of Clan Highforge. Sadly for Mukluk, his talents were not with any notable dwarvish obsession: not smithing, nor drinking, nor brewing, or nor wrassling, nor anything remotely fun. Mostly, he didn't like other dwarves too much at all.
Proving his parents right, Mukluk squandered opportunities from the 2nd cousin ring of family, and then back to the 4th cousin ring, and finally close enough to be entirely rejected by the Clan leadership itself for his lack of dwarven talents and potential.
They didn't think he had any. Mukluk found it hard to argue. According to dwarves, he didn't.
But Mukluk's true secret was that didn't care much what they thought. Stubborn to a fault, he liked what he liked and was going to do what he was going to do. Finding some small connection to his favorite mule, Moose (a name that might get passed on from favorite mule to next favorite mule), Mukluk started working on his own path: trading and traveling. He's decent in trading, and surviving, and has made a good habit of spending the last decade or so as a traveling tradesperson. He largely moves vegetables, seeds, and different seasonal vegetables from place to place. He'll occasionally join a caravan to Magnimar or Riddleport as a way to make money and move his wares, but mostly his home base is Sandpoint.
He's known and trade with Koya for years. She's pretty much the one in Sandpoint who could stand Mukluk, or at least accept him for what he was. She was easy to talk to, and often saw the world as he saw it. And because he never felt much affection from his parents, whatever support and kindness came from Koya filled him with a measure of joy that Mukluk takes as family.
Mukluk has had the usual training path for a dwarf: he has received the usual weapons training, some shield & armor training, but very little of it has really stuck.