misalliance
From Longman Dictionary of Contemporary Englishmisalliancemis‧al‧li‧ance /ˌmɪsəˈlaɪəns/ noun [countable] formalSUITABLE# a situation in which two people or organizations have agreed to work together, marry each other etc, but are not suitable for each other It was a hopeless misalliance.Examples from the Corpusmisalliance• The dominant supporting character is Lady Davers, who supplies an analysis of society's reaction to such a misalliance.