Minato occupies the slot called “Parent” or “Older Brother Figure” or “Mentor.” Or rather, all three.
The reason Kei is Kakashi’s “Anchor” is because the term can be used two ways. Both as a point of stability–what with Obito having vanished after Kannabi and Rin not actually being on their team–and as an occasional dead weight that might be considered holding him back.
Such is love.