Believe it or not, such a phenomenon exists and can be a trap for the unwary. Collaboration is what brings about the best ideas. But who owns those ideas and how does a person gracefully discuss the ownership topic with their collaborator? The answer, very carefully and, hopefully, in the beginning of the relationship.
Under Copyright law, the default rule is that joint owners need to account to the other for any royalties earned based on the work of authorship. Under Patent law, a co-inventor does not need to account to the other co-inventor for royalties earned based on the co-invention. Trademark law is similar to Patent law.
As is often the rule, the situation will dictate the preferred way of addressing the ownership issue of intellectual property rights. But, it is often better to address the issue up front, than to wait and address the issue after the invention, work of authorship, or brand is developed.