DNA information on those profiles of non-family wikitree members. was removed under the EU GDPR rules. (As of 25 May 2018)
The only way to get it back is to invite your brother to join Wikitree so that he can re-enter his own DNA details. Noone else can do it for him.
THere is a thread floating around G2G that discusses the rules and the effect they would have on wikitree.