sismfreq is right - unless you two agree basic discipline rules this will never work and he will play one off of the other.I had a massive problem with my b/f when we first moved in as he would tell my son off for things but let his daughter get away with the same thing!! I had to sit him down and talk rationally,being very careful to not have a go at him,and come up with some ground rules that we would both stick to.And I would tell my son that I was very proud if he told me the truth,even if he had done something wrong,as big boys always owned up.