Hi OP I'm sorry that you are going through this. It's awful when you meet someone and fall in love and other things conspire to keep you apart.
I've been in a very similar situation. My children were 12 and 14 when I met my partner. His 3 children were in their early 20s and left home.
It was extremely difficult balancing my relationship with my partner and my children. We didn't move in together and always lived separately. My DC liked him a lot.
My kids went through turbulent times during their teenage years and it was extremely tough. There's no way my DP could have lived with us. He was around a lot and stayed over some nights. However he could always leave if they kicked off.
My DC are now 19 and 22 and have recently moved out. I was delighted to get some freedom. One of my DC developed a mental health illness and her behaviour can be unpredictable and sometimes aggressive.
My partner was very supportive but he was pushed to the limit by her behaviour.
I had thought all along that things would change and my DP and I would live happily living apart. We get on like a house on fire.
This morning was stressful for me trying to sort out some financial stuff. My partner was here and noticed that DD had turned off the internet and had knocked the box off the wall leaving it hanging by the wires. He was cross over her carelessness which is extremely common. She is chronically careless.
He blamed her (she wasnt here) and we got into a row culminating with him storming off. He doesn't usually react like this.
I truly believe our relationship is put under undue pressure by the fact that his DC are adults living away from home and my daughter is still causing disruption. My son could return home and his lifestyle involves a lot of late nights etc.
My DP has reared his DC and doesn't need this crap. To be 100% brutally honest I wouldn't have got into this relationship had I known how much trouble my DC have caused and how much it impacted on my partner.
I understand how your partner feels. It's really sad because you sound like you really care for one another and you are both decent people.
I understand where both of you are coming from and I struggle with it.