[mothered]

it was delivered to me and a few minutes ago I claimed DNA

What type of verification (If any) was provided on delivery?

the representative has opened an investigation that lasts 5-8 days, will I get a refund?

Can't say without knowledge of the DNA events.

If DNA fails, will I be able to return the item?

Yes.

Simply say that your brother accepted the package In your absence, and told you about It after the claim was submitted to the company.