There is a very real danger that you will get caught in the middle, especially if the ex-spouse is not a Christian or has walked away from the faith. On the one hand you fear to displease your spouse while on the other hand you worry about rocking the boat with the ex-spouse which in turn might cause ugly confrontations. Another consideration is the resentment the child may feel toward you and the specter of the sullen, unhappy child in your care may be enough to have you make compromises that sooner rather than later turn into Faustian bargains.
1. You need a clear and concise understanding what the rules and regulations are that you must enforce, especially if you did not make them. Humble yourself and ask the ex-spouse exactly what it is you are supposed to do. Proverbs 12:1a teaches that a person who loves discipline also loves knowledge. By inference, you cannot have one without the other.
2. You must be united with your spouse in her/his parenting of the child. Even if you disagree, in front of your stepchild you must present a united front. Proverbs 11:29a explains that bringing trouble to your family is a useless undertaking. Take this Scripture to heart and you will have peace in your home.
3. Cultivate the ability to be the calm one in the room, even if your stepchild pushes each and every button. Proverbs 12:18 admonishes that reckless words will do great harm while wisely chosen words are going to bring healing to the relationship.
4. Be willing to be unpopular. Sure, you want your stepchild to love you and sing your praises, but in a pinch you need to have the ability to put the needs of your ego aside and do the right thing for its own sake. Proverbs 18:24a warns that a mindset that refuses to rock the boat and instead sinks to people pleasing will lead to ruin.