What age do kids start playing divorced partents to manipulate what they want?!

What age do kids start playing divorced partents to manipulate what they want?

My girlfriend, and also mother of my 6 month old, has 2 kids ages 10 and 13, from a previous marraige. They spend close to half of the time with us and half the time with their dad. Lately, I have had a hunch that the 13 yo is manipulating things so that we get into a fight. Yesterday was the first day back with us, and the 13 yo chose to spend the night with a friend. We got a call today from the 13 yo and she was asking to be picked up because she wanted to spend some time with her mom. When she got picked up, she asked if the same friend could spend the night, but it was not possible because we were staying an hour away at my house. After they all went shopping for a couple of hours, my girlfriend and I were in the smoke room talking less than 5 minutes when we were interupted 2 times always by the younger one. The second interuption was this. "mommy, after your done can you come spend some time with us?" I claim bs. What do you think?

You have come into their lives uninvited, take up a fair amount of their mother's time, and have fathered a sibling they didn't ask for. Of course they are jealous and causing trouble. Thirteen year olds are difficult in the best of times. Mom needs to spend as much time with them as possible but still set limits. She should have said something like " We're talking now. We'll be done in ten minutes. Please don't come in until I call you." Stick to the ten minutes and then give them more attention. Let her do the disciplining as much as possible. You are entitled to be treated with respect but that doesn't mean they have to like you and the quickest way to ensure that they don't is to communicate that you don't like them.