Wikitree doesn't record DNA data, just the fact that a person has taken a DNA test and which one(s). That information propagates backwards and is noted on ancestors' profile pages. If your brother is living, only he can add DNA test information to his profile. You can invite him to become a member, he can add the information, and then turn his profile back to you.
If you have his permission, you may want to add that raw data to a site like Gedmatch. That site lets you compare data, not just ancestors.