The weirdest Seed design analysis so far: their beards!
It is highly probable that he trims his mustache regularly. The mustache line above the upper lip is very even and neat. The mustache line under the nose is also as symmetrical as possible and has a minimum of extra hair.
There is an indentation under the lower lip: this usually indicates manual hair removal (shaving). You can compare this part of the beard with the beards of John's brothers: there is no indentation under their lips.
Next, we see a neatly trimmed area on the chin (two almost symmetrical semicircles). Usually this area in men is characterized by alopecia of any degree (like the supra forehead area), but given the well-groomed nature of the area, we can also assume that John additionally shaves it.
From the side, we can see a continuous line of growth from the mustache to the beard and then to the sideburns. We can also see sparse hair above the beard line: this tells us that John shaves this area regularly (usually once or twice a week, judging by the length of the hair).
John shaves his beard from the neck down: we can see the dots characteristic of hair after shaving. But he does not shave the lower part of his chin, perhaps finding it tasteless.
Addition: John regularly shaves the back of his head. We see a neat, artificially shaved hairline.
Addition 2: John's hair tends to curl. They are dense and curly where he does not straighten them (beard, back of his head). This dense arrangement of follicles indicates that John is unlikely to go bald by old age, and is also likely to have high body hair growth. But since we don't see any hair on his chest or arms, we can safely assume that he removes body hair. He also has the thickest hair among his brothers. Given their tendency to curl, we can assume that the humid weather greatly affects the condition of his hair.
Our next victim is Jacob:
Unlike John, he takes little care of his beard, favoring more natural hair growth. His mustache is more asymmetrical and messy, its length extending beyond the border of his upper lip. There are bald spots under his lower lip, which is natural for men. Given the points on his skin, he also shaves this area additionally, artificially separating his mustache from his beard.
This is most likely due to the burns on his face: he has to keep his beard starting from a certain line of his face, otherwise it will grow unsightly and have more bald spots.
Jacob shaves regularly, but he mostly shaves off the areas around his beard, and hardly touches the beard itself. He makes sure that his beard has a strictly defined contour and matches his temperament and views.
He doesn't shave the neck area. Unlike John's, we don't see any shaving marks there. However, we know from the cut-scenes that he uses a trimming knife so his beard in the neck area does not look overly long and messy.
He keeps the hair on his head under strict control, shaving all but the top of his head. This is most likely due to age-related alopecia and burns, which caused his head hair to grow mostly poorly.
Compared to his brothers, Jacob has the least amount of follicles. Firstly, he is a redhead, and secondly, he is the oldest among them and has generally experienced comparatively more stress in his life. We can see that his beard is sparser and more transparent on his cheeks than on his chin.
Addition: there is also the possibility that his hair fades in the summer and becomes similar in color to his eyebrows. It is likely that his body is mostly hairless except for his private area and legs.
Addition 2: his hair is straight and coarse, and very manageable judging by the styling on his head.
Joseph's beard is shorter than his brothers. His facial hair is sparser, and we also see more shaving marks on his cheeks. We can see the even growth line of the mustache above his upper lip, as well as the characteristic shaving marks on his cheeks and chin.
He deliberately leaves the chin itself untouched, allowing the beard to grow there to the required length: this makes his profile more imposing.
However, on his cheeks and above the lip he either shaves or trims the hair because it is much shorter and sparser.
He also shaves his entire neck down to his jaw line, unlike his brothers. And he trims the beard on his cheeks at the jaw line, preventing it from growing lower.
In terms of follicle count, he's in between his brothers. His hair is quite thick for his age, but he is prone to baldness to one degree or another.
Addition: he does not cut the hair on his head. We can see the age-related alopecia characteristic above the forehead, but the very top of his head and the back of his head are covered with thick and long hair. They are visually clean, but not groomed in the context of any haircut.
Addition 2: his hair is likely the softest among his brothers. They are not frizzy and are not prone to coarsening and sectioning.
