Please tell me, are congenital cataracts in teenagers rare?

No.: Congenital cataracts affect about 25% of the population. But remember that any opacity in the lens on the eye is called a cataract, so most congenital cataracts do not affect the vision. They are just small opacities in the lens that do not get worse or affect vision.

Yes: Congenital cataracts are rare. Cataracts in kids/teens are rare too. Usually a systemic work up is involved to make sure it's not secondary to another disease process.