Am I wrong to my step daughter to look after her half siblings for a couple hours?
If she has nothing against it, there’s no reason for you to feel bad. Ask your husband why it bothers him. Tell him that if he’s not willing to allow his daughter to babysit for a couple of hours, then you need to find a permanent (paid) babysitter that you can call whenever needed. Your job is important too, and if you need to leave the house every once in a while, it’s important you find a way to do so. – May I remind you that most babysitters are between the ages of 15 and 18, just depends how responsible they are.