Geno is owned by both nintendo and square enix, square enix said this in a massage this year wich means he is a 2nd party so nintendo are able to use him without needing square enix plus they already did that in super mario-kun comics
m.ign.com/articles/2013/08/13/… IGN interviewed a couple of Alphadream execs who helped make Mario & Luigi: Dream Team who elaborated on the proper way to go about giving Geno and Mallow minor roles in future RPG games.