[I want to add a group member as an owner to my group.]

I am trying to make a group member an owner of a group I own.  I went into Group Information

then Members & Roles

then selected the name

then checked the owners box and clicked Apply. 

I received the message, You are about to add group members to the role of Owners... Are you sure you want to continue?  I clicked yes but it did not work. 

Someone please tell me what I am doing wrong?

Thanks, Dori