Male kitten anatomy

Ok this may be an odd question... I've never owned a male cat before, always females. The only male cats I've had were very young foster kittens. I now have a foster kitten who is 12 weeks old.
My question is, are the testicles supposed to be descended already at this age? I thought that was something that happened when they are older? I'm wondering because he is also very large for his age, he's already 4 pounds and not overweight. I don't think he is older than the vet's estimate because his teeth development matches the vet's estimates of his age.

Radar definitely had all his male parts in the right place when I got him at 8 weeks, and Sonic's were quite prominent at 13 weeks when I got him! 4lbs is large, but don't forget that as a male he will likely end up bigger and heavier than his female siblings, there can be quite a difference between male and female adult weights and sizes. I only have boys, smaller ones at that, but when I go to cat shows I am always struck by just how much smaller females of the same breed are

Patches was an orphaned kitten that I got from a coworker when he was about four or five weeks old and his were already descended. I remember I took him to the vet for a check and she checked to make sure he was male. She said he's definitely male, they're small but definitely there.

Sorry, I don't have an answer to your question, but I hope you don't mind if I piggy-back on your topic with another question about male anatomy. This is a really bad question that I feel really idiotic asking, but am just going to do it anyway....does a neutered male have any external sex organs to watch out for? My long-haired kitten's fur has grown longer and there is more of a need for me to do some grooming in that area to prevent mats and poop/litter from getting stuck....I am not really familiar with the male cat anatomy (I just never looked) and don't want to hit or scratch anything hidden in all that fur when I am using the metal comb.

Neutering a cat is castration so they don't have any testicles left. They still have a penis of course but you don't have to be concerned about that, they usually keep it inside except every once in a great while I have seen Patches with his out cleaning it.

I just finished an externship at a large humane society where we would neuter upwards of 3-10 cats per day. We would spay/neuter as small as 2 pounds, and all but one cat had both testicles descended during the three weeks I was there.

The little sacs where the testicles used to be are still present on male cats after neutering. They usually shrink down and get harder to notice--it looks a lot like kitten anatomy, actually. But I could still tell, on Tiny and Daffy after they were neutered, that they were male.