I'm 39m and i've been with my partner 40f for just over 3 years now and we've been living together for just over two years. She has two children 12 and 9 and we have one together who is almost 2. I didn't have children before so becoming a step dad to two children was both daunting and challenging for me. I have a great relationship with the eldest as he loves football and has always been quite talkative. It's always been much more challenging with her youngest as she didn't want me to live with them (which is understandable as she was 6 at the time and parents had split up a number of months before). After I moved in things were fairly fine, I still struggled to build a relationship with her as she is very close to her mum (again understandably), but she was very quiet and reserved at times so doesn't interact much when I try. She loves gymnastics and is very good at it so I was able to help her with that and we'd make up routines in the garden and she'd basically climb all over me doing various gymnastics moves, I also helped spot her as she's got older and learning new moves. However, not long after I'd moved in she used to come and get in bed with her mum and me at night, three in a bed is a bit of a squeeze and eventually I was asked to go and get in my step daughters bed when she came in. I didn't mind at first but this quickly became every night and then progressed to going to bed in her bed, which was a small single bed. After a few months I raised it with my partner who then revealed that her daughter had never slept alone. As I began to ask when she was going to address this and try to get her sleeping in her own bed I was met with anger and resistance. As time went on and my stepdaughter got older she became very rude and has continued this towards me, my partner rarely addresses it and when I respond by asking her to not speak to me that way or to tell her to stop being rude my partner doesn't like it. My partner eventually started getting my SD to try and go to bed in her own room, this caused huge outbursts and meltdowns of screaming and hitting my partner etc and the process stopped. We then had our own child and I managed to sleep in our room with my partner and our baby for two weeks before being forced back into SD's room and being away from my child as she was in a snuz pod next to my partner. My step daughter, now 9, is now ruder than ever, even towards her mum, the meltdowns are off the scale and more and more frequent, she often wakes the baby up by screaming and slamming doors. She swears a lot during the meltdowns and sometimes even just in general. We think she may have ADHD which will massively play a part in some of this but I also think my partner's inability to recognise and challenge naughty behaviour is not helping. She doesn't give consequences or may threaten consequence and not follow it through. She quite often buys SD something in order to stop the behaviour which infuriates me more. I'm now at a stage where i'm worried about how it is affecting my daughter, I also really struggle to live with the rudeness and naughty behaviour the rarely gets addressed and i'm not allowed to get involved with. I feel like I want to end the relationship but doing so would mean I can't protect my daughter from these meltdowns as I wouldn't be in the house anymore. I don't know what to do