Marriage is VERY complicated as it is, but if you throw in merging two families with kids from previous marriages, welp, that's a whole other level of complicated. See, the thing with getting re-married is that there need to be clear boundaries for the step-parents. Finding the right balance in step-parent and step-children relationships is not easy but one thing that the step-parents should always remember is that they are in no way entitled to someone else's child. You might be joining a new…