Biting Bugs? Family going crazy, help!?

[Danielle A]

I just adopted a stray kitten, took her to the vet, and found out she's perfectly fine.
But apparently my Dad doesn't think so.

He's constantly complaining about these biting buys, tiny enough to mistake for a crumb. He says they bite like crazy (enough to keep him awake at night.) My Mom and I don't feel them hardly ever, but my Dad does.

Anyone have an idea of what it is?
They're very tiny and a brown color.
I don't think they're fleas, my Dad found one and showed me. I know what they look like - and it didn't appear to be one.)