The sesamoids are right where they belong, being part of a tendon system. What has happened is that the 1st metatarsal has gradually moved "inward". Instead of its head being centered over the sesamoids, it is now 'off-center', and severely so. That muscle/tendon system is now functioning like a bow string to reinforce and induce progression of the deformity. The only fix for this is surgery to restore the metatarsal position. That doesn't mean that you need to
have surgery, only that surgery is the only possible way to correct the issue. This is an extremely common finding. Most people get on well with this problem.
The deformity is cause by many years of over-pronation while walking.
It
looks to me like you may have some instability in the area of the Navicular/1st cuneiform joint, but only a physical examination and gait analysis would tell for sure. If so, this would very definitely contribute to over-pronation.
Are you having any symptoms in front of your ankle? It looks like your anterior tibial plafond may be under some stress.
Here's an image with correctly aligned sesamoids:
Understand that feet are as unique as faces. As far as bunions (Hallux Valgus) being hereditary, I've never heard of a gene coding for this. What is inherited are osseous shapes and alignment patterns that predispose one to developing such a deformity.