Dimple is the result of facial muscles not attaching to part of the skin. Because of this, some dimples can be temporary as they appear and disappear with age. However, there are limited evidence that dimple is inheritable and this likely is a myth. You can learn more myths of human genetics in Professor John McDonald's website.

That’s an excellent question and many scientists have wondered that as well. The University of Utah's Genetic Science Learning Center refers to dimples as "highly heritable". That is to say, while it is likely to pass and show from parent to child, this inheritance is not as clear-cut as autosomal dominant traits like Huntington’s disease. They are instead considered an "irregular dominant trait". The likely case for why it is not completely predictable may be because having dimples is controlled by more than one gene.

23andMe is a good place to find a reliable answer to your question:

Dimples

People used to think dimples came from a single, dominant gene inherited from a parent. Now, researchers know this cherubic trait is more complex.

My younger grandchild has a really strong dimple in her chin. I was excited to find a photo of myself with a dimple in my chin, though I don't usually show a dimple in my chin. This is another example of the complexity of dimples - that I had a definite chin dimple in 1 photo, but I don't usually look like I have a chin dimple. I had a big smile in the dimple picture.