My dad has been with this woman for about 13 years (since I was 4). This woman used to live in a horrible flat behind a prison in one of the worst/roughest areas of the city. My dad started living with her until she got herself pregnant, by which point my dad moved her into one of the posher houses he owns (he is a property investor).
She has taken away all my childhood momentos and given them to her children. e.g. She told me and my sisters to bring around all our disney videos (bearing in mind I was a kid then and still enjoyed them) she kept them for her son and she kept changing the subject whenever I asked for them back. I also fixed my nintendo 64 and as soon as I told my dad the good news he asked me to bring it over and then I never got it back again. They have all this stuff that is actually precious to me and my sisters despite the fact they literally have thousands of toys of their own among them. In fact, I know my stepmom wanted a girl among her flock (ha, she didn't get one!) and she actually STOLE all the dresses I used to wear as a little girl and she kept them for herself in case she got pregnant with a female baby. I didn't even know she had them, I just remember my mom asking where several of my dresses had gone, I didn't think anything of it until I found them in my stepmom's room when she found out she was pregnant again (not knowing whether it was a boy or girl yet).
She then popped out another child and moved my dad hundreds of miles away from me to a house in the countryside. She stopped working and completely relied on my dad.
My dad told me he didn't have enough money (he does) to send me to a private secondary school like he did for my older sisters (they were old enough to already be in secondary school by the time her child came into the picture). I then found out that my stepmom had sent her two sons to private schools (who were born after me and live in the middle of nowhere anyway?!). My mom called my dad to ask about this but he denied it (even though my stepmom told me herself).
My stepmom didn't know that my dad gives a small amount of money to my mom to help out with us (as she is a single mother with 3 children), but when she found out she completely flipped out and stopped talking to my dad. My dad still helps out with money but now he barely gives any because of my stepmom. My stepmom wouldn't even allow my dad to buy a suitcase for me when I was going away, and she went completely mad at him when I let it slip that my dad had bought it for me.
This stepmom also stopped allowing my eldest sister to visit my dad for about 2 years because she thought my sister was 'ungrateful' because apparently my stepmom thinks she is like the mother we never had. To explain this, she is always bad-mouthing my mother, constantly saying she is irresponsible and completely exaggerates our "difficult" situation to my half-brothers.
She is constantly rubbing it in my face that she has a better lifestyle than me, my sisters and my mom- even though its thanks to my dad divorcing her that my stepmom has anything at all!
Her and her eldest son (my half-brother) even started mocking me for not knowing the name of a particular fossil he had in his room. She tries to make her sons better than us and has definitely made sure that anything we got as kids her kids get twice as much.
I absolutely hate her guts. She is living off the money MY DAD earns, thinks she has a right to control if he gives us money for necessities or send me to a good school and she thinks she can act like a snob towards me! I hate her. I want to see them split up and see her trying to raise children on her own with no financial support from my dad. See how she likes it! She is constantly trying to make me feel bad about the situation by pushing further if I don't give her the obvious response she wants. I'm scared to say anything to her directly because then I fear I won't get to see my dad for who knows how long. How can I break them up? She is a complete leech.
FYI, they aren't technically married. He didn't propose.

