No, none of what you describe is legal. He cannot add someone to the LLC without your consent because it reduces your ownership interest, and he cannot reduce your ownership interest (take away something you own) without your consent. (Note: he could have given someone else part of his share or interest in the company, since then he is just reducing what he owns and not affecting you.) Also, in a 50-50 partnership, which is what you apparently had, neither partner can unilaterally make a major decision without the other, since neither one has majority control. The adding another person would be void. And in a 50-50 partnership, since neither partner is a majority owner, neither has the power to dissolve the business with the other one's consent.