Question on Primeness-well kinda-South vs. North

So here is a question for all you guys who talk about primeness and daylight etc..

We have 2 dogs-the same breed-Shiba Inu's-Todd and Kevin-they were both bought in Missouri as pups,but after 8 weeks old have both lived in Canada their entire lives.Todd is 5 years old and Kevin just turned 1.Todd has a very full coat-heavy underwool and all-Kevin has absolutely no underwool at all-just hair.He has been shedding up until a day ago.They are both healthy and happy dogs.Why would Kevin the dog that is a year old be so screwed up with no underwood at all?( especially this time of year) I get they are from the south-but what would cause him to have no wool yet-age? Or are there some of you out there that may have a scientific answer as to why he has not yet developed heavy fur.Is it because of the genes of the dogs being born in Missouri or am I nuts here? Do any of you think it will take a few years to get his fur fully developed-as I don't recall Kevin having this issue.

Just spit balling here wondering what kind of answers some of you guys may have?

Could be age. Keep track over the years to see if Kevin gets underwool sooner each year as he ages.
Is Kevin an indoor dog or indoors most the year?

They are indoor dogs but go out probably 4-6 times a day.

Yeah, I think age is the variable in play right now. If the difference persists in year 2 and 3, then there could be a genetic thing.

It's the same with wild animals the young critters will prime a lot later then the older ones.

i agree with the beav. i caught a young of the year coyote two days ago that the leather was still blue, and in the other trap a big male. snow white hide, extra pale, heavy coyote.

I agree with Beav as well. Now their are variables to all things. I believe if a yoy animal is born first in your area, he may prime sooner than the last one born in the same area. And their are countless more variables. Just how nature intended it. But it does make for some good conversation
Just my thoughts

Most all young animals do not have a fully developed endocrine system. My guess is that Kevin will become more like Todd as he ages. If he doesn't...you might mention it to your vet. Maybe a blood test will show he is lacking some hormone or has a dietary deficiency.