My girlfriend and I have been together 3 yrs, our son is 1. She had children already ages 12, 8, and 5(current ages) They have always caused issues with their behavior,  we moved in together about 2 months ago, and its been bad since day 1. I've been asked to be disciplinarian, but when I do it causes problems. It's fine for her to say I'm gonna get mad and come in room to scare children as a threat but as soon as I say anything or even raise my voice I'm the bad guy. When I bring subject up, its immediately met as saying she's a bad a parent which is not the case. She had her first child at 16 by a 25 or 26 yr old. Her parents never stepped up to try and show her the way to do stuff, but instead just let the kids run the situation. We have been fighting 6 out of 7 days, the one we're not is usually when the other kids are not here. I dont want to just give up and throw in the towel. I love her, and even her kids(she doesnt think so) and that's why I'm tough and have expectations for them. I want to see my son grow daily and not though pictures or videos on social media. I may have just needed to vent or get it out but anyone had a similar experience, how did it end up? Ive never been on a forum or anything, not sure exactly how it works. Please and thanks