Do people with pronounced cheekbones have stronger jaw muscles?

No. If anything, as I explain below, more prominent cheekbones might be correlated with a slightly weaker bite.

Let’s begin with some basic skeletomuscular anatomy. “Cheekbone” is the colloquial name for the zygomatic bone, highlighted here. As you can see, if you touch (palpate) the lower lateral corner of your orbit (eye socket), the bone you feel there is the edge of the zygomatic bone. If you palpate upward from your molar teeth until the skull flares out, that’s the lower margin of the zygomatic bone.

I like your choice of words, “pronounced cheekbones,” better than the common expression “high cheekbones.” These bones can’t get any higher than the margin of your orbit or they’d obstruct the eye. I haven’t given a lot of thought or analysis to this (much less made a comparative study of skulls and ethnic groups for this trait), but it seems to me if someone is described as having high cheekbones, it really means the face below the zygomatic bone (the maxilla especially) is a little longer than average. The women below, in my opinion, are better described by your expression, as having pronounced cheekbones rather than “high” ones. The bones flare outward more, rather than being higher on the face.

For the purpose of your question (bite strength), there are two pairs of biting muscles to be considered. (I will omit two other pairs that produce the side-to-side grinding actions of the jaw.) One pair is the masseter muscles and the other, the temporalis muscles.

The temporalis muscle has no connection to the zygomatic bone. Its tendon passes behind it but it has no bearing on your question. It arises, fanlike, from a ridge above the ear and its tendon ends on part of the mandible called the coronoid process, so when it contracts, it lifts the mandible.

The masseter muscle does arise from the zygomatic bone, so it’s the more logical focus of the question at hand. (I added the yellow arrow and I explain that further on.)

Unusually prominent cheekbones, though, would only increase the length of the masseter or its tendon. The strength of a muscle isn’t determined by its length, but by its thickness at the widest point. Thickness is proportional to the number and size of the muscle fibers and they are what determine contraction force. On that principle, this is why a big biceps muscle in the arm is stronger than a small one.

I don’t see reason to think a slightly longer muscle, in the case of a prominent cheekbone, would be any wider or stronger. It might even be a little bit weaker (although not significantly so, I would think).

Let’s consider that masseter from an anterior view and some principles of biomechanics. Below left, I’ve taken an image straight from Google Images and superimposed a vertical black line and another along the axis of the muscle. The angle between these is 20°. If the masseter were oriented straight up and down, it would exert its full force (100%) on the mandible. But being at a 20° angle to it, it exerts only 94% of its force on it. The force exerted by a muscle is a function of the cosine of its angle of insertion; cos 20 = 0.94.

Now on the right, I stretched the image a little bit to crudely simulate how the angle of insertion would change if the zygomatic bone projected more laterally, as in the women above. (Ignore the distortion of the upper head—not my intent but unavoidable in my crude manipulation of the graphic.) Even as much as I stretched this, the angle of insertion changes by only 3°. The cosine of 23 is 0.90, so in this case the muscle would exert only 90% of its force on the mandible—a little bit less than in the former case.

For that reason, everything else being equal, we can at least speculate that a wider flare of the cheekbones would slightly weaken the bite force.