My son seem to have grey hairs and some hairs with grey hair tip. Why and what c!

My son seem to have grey hairs and some hairs with grey hair tip. Why and what can be done ?

We are worried that our 3 year old son is starting to show grey hair. What are the possible reasons ?
Once accidently when closing the trunk, trunk hit him. But since he was ok after sometime within a day Doctor said we don't need to come. Can this head injury be the reason ? There was no lump, no loss of conciousness. Can any Docs advise ?
We beleive he is getting sufficient vitamin supplements.

4 weeks ago
Both my wife and myself started having grey hairs around 14 years. Could this be genetic ?

I have an uncle who's hair was completely white by age 24. He was a grey haired teen. At least he still has a thick head of luxuriant hair, even in his late 70's while most of his friends are balding.
Your son is likely experiencing that wonderful thing called genetic variation. If your doctor feels that there is nothing wrong with him nutritionally, it's not something to worry about as it's just a cosmetic feature.
The blow to the head is likely unrelated.