Those related artists are generated automatically by algorithms that detect what other users listen to alongside your music. From the Artist FAQs:
How are the artists on the radio and related artists populated? Spotify's related artists and radio are determined by algorithms which look at what people listen to alongside your music. So if I put your music in a playlist alongside artist X & artist Y then artists X & Y are more likely to be shown as related to you or played on radio. There's no manual way to change these. You can start to affect it by creating a sharing playlists of your music with other music you think is more related. This will increase your streams and the bands you want to be associated with, increasing the chance of them becoming related artists.