How do you control a brat that is not your child?

Hi,
You (both) created a "composite" family with many potential innert difficulties / obstacles.... I have the feeling that you didn't plan how it will work (but hit the road and hoped it will work somehow).  It won't work unless you (both) set the rules and determine the proceedures.  Like it or not you MUST discuss that matter with your partner.  It is of utmost importance if you really want that you'll all work as a family / union.   You (both) have to undertand that without setting the rules it will sure fail and situations as you described will occour every 2nd day (if not every single day !).  Above all, once you set the rules you (both) will have to stick to it and not let any "discounts" or "by-paths".  5 persons depend on it, give it a chance.
Best regards,

As a single father, I know that sometimes I let my children get away with more things than I should and I know it's because I am trying even harder now that their mother and I are no longer together. It sounds like your boyfriend is overcompensating for the lack of his daughter's biological mother being present. But this is not an excuse for allowing the child to sabotage your relationship. I think you need to really discuss this with your boyfriend as this type of behavior will only get worse if it is not addressed immediately. Good luck!

1st off talk to your boyfriend about how you feel.  Don't point fingers just simply state what you have stated here...but show the respect to do it not in front of the children.  They don't need to see the adults argue, especially over them.  Many times when kids see that they then start pitting one against the other.  So don't give them ammo.

 2nd talk to your boys.  Let them know you do not find her behavior acceptable and you will not accept it from them. 

3rd unless your boyfriend is on board with you disciplining his daughter you could be in a lose lose situation.  If he will not support you by making his daughter be respectful of you and the rules then maybe you need to look for a different boyfriend.  If he will not make his daughter respect you are you sure he does is the thought. 

 There is a question in my mind that is not addressed in your question...does she live with you all the time or is she there only for visitation.  If it is just visitation perhaps those days you simply take your boys and go elsewhere, if possible, but still talk to your boyfriend.  If she is there all the time then the above 3 steps need to be considered. 

I have one question. Why don't you say no to him when he asks you to do something you already said you were not going to do?  Calmly explain that had you not told her no, it would have been up for discussion but since you did, it would be a bad influence on your boys if they saw that whining would get their way.  It is probably harder for him to say no to her if he is just now trying to form a relationship with her and does not want to make her dislike him...I don't agree with this, mind you as I think he is setting a pattern for himself (and you are allowing yourself to become a part of it) that will not get easier as she gets older but harder and harder.  You really would do you both a favor by putting your money where your mouth is and being a good example to him by saying NO (even to him). Take care and good luck.