I think one of our kittens might have ear mites.

He has quite dirty ears and he is scratching quite a lot.

Is this something I should take him to the vet for, or is there a way i can treat it at home.

He is about 3 months old, and his 2 brothers seem to have very clean ears.

Best to take him to the vets where they can do a quick test for ear mites. When one of my cats was a kitten she had lots of wax in her ears & I thought it might be ear mites. Turns out she just had dirty ears. My vet gave me some drops (which she hated) but she seemed to grow out of it. Best to get your kitten checked out though.

Yes, go to the vets. They can look properly in the kitten's ear to see what is going on. Don't leave it, ear infections can set in.