Masturbation with my sister underwear. I want to get some help-please help?

Hi. I think, you understand that you need to stop this and knowing this is a good step. I am not aware of what led to this and if you have tried anything to stop this or not, so I'll try to answer considering possibilities. Growing up can be hard at times because you get aware of a lot of things. In case there are any thoughts or feelings that are behind this action of yours, then you can try working on them. You can calmly gather your thoughts and think about how you need to actually act towards your sister and then, once you get the right course of action you can do that and try to reinforce it. You can perhaps try to control the urge when you feel like masturbating by either trying to distract yourself or by reminding yourself that you shouldn't be doing this or by slowly decreasing the frequency. However, this will take time. You'll be knowing what will work best for you so I hope that you'll be able to take the necessary steps and get out of this. In case you need to talk more or you have tried everything listed, you can message me. Good luck.