my sisters parenting drives me insane...

I'm not one to judge someone's child or parenting; but my sister drives me insane. (I'm still living at home while my bf is on a 8 month long deployment.) She got pregnant at 14 and had her son at 15; she's now 17 and her son is 2. She's terribly irresponsible. She goes from boyfriend to boyfriend. Is focused more on what ever boyfriend and being a high schooler than a mother, I know she's young but she's had him for two years now that she's done none of the work, my mom does everything. My mom lets her walk all over her. My mom sleeps in the living room with her son, and has since the day he was born. Been sleeping on the couch for 2 years now. My sister sleeps in a totally different room; I understand for the fact that she has high school still and needs sleep (which is my moms excuse for it), but even during the summer and on weekends, she doesn't even help out or take him for nights. She'll sleep until 1-2pm too leaving him with my mom. As soon as she comes home from school she instantly naps too, leaving my mom with him for even more time, she gets no time to herself. And she is always focused on whatever new boyfriend she has. She throws fits too if he's not aloud over. There was one day that dinner was done and she hadn't fed her son all day, she comes in the dining room with a plate she made for herself and her boyfriend; nothing for her son. My mom said something to her and she insisted she was just gonna share her own plate (she wasn't going to). She got the iud because my mom insisted, and she's still trying to get pregnant with all her new boyfriends. I know this because I have found a new test with every boyfriend she's had and they've even told me personally that they don't use protection wth her. I've told my mom and she just lets it slide. She also always says how badly she wants a girl and can't wait to have one one day, she always says she wished my daughter was hers; and she posts photos of her, her bf and her son saying "our little family". Mind you, her boyfriend could give two shits about her son too. He would agree to watch him so my sister could shower and ends up avoiding him and having my mom watch him, or he won't be watching him and he'll get hurt or get into things he shouldn't be because her bf couldn't keep his word. She always tries to take my 5 month old daughter and cuddle with her and her boyfriend and totally exclude her son; she wants a little family of her own since her sons father is hardly involved. She avoids her son and hands him off to anyone. Completely neglects him. I remember one day specifically she came home from school, walked right past her son and picked up my daughter saying "hi I missed you!" She would take her sons child support and spend it all on her boyfriend; he would order takeout pizza, order him clothes, spend every dime on him and on for her son so my mom started taking it. Her and her boyfriend felt no shame using them money on food for themselves. My dad buys my nephew EVERYTHING he needs, always bought his baby food, formula, still buys his milk for him, diapers, wipes. I get it because she is a junior in high school, no job or license. But still.. she never even tried to help with the child support (mind you the child support was dirt, he was paying 50$ a month because he claimed he was going to colleges, which he is not and just quit his job, he's missed so many months too). She takes her anger out on him as well.. whenever her and her bf fight or break up she takes it out on her son. She'll scream at him for nothing and she even calls him "that kid, listen kid, omg kid". He'll just want attention or to play and she has not desire for him. She is glued to her phone 24/7 or her bf. She's been so focused on her phone while he's running around getting hurt etc. My mom has put her foot down but caves into any punishment she gives. My mom won't even allow her to get her permit because she's so irresponsible and not trusted. The list goes on, trust me. The only thing my sister does is put him to bed. Which brings me to the point of this post, I really can't stand the way they raise him. And no, this isn't some mean judge mental parenting post. I believe every mother is entitled to their own parenting techniques, but they way they raise him I really don't want to be raising my daughter in the same environment. They let him hit, scream, bite, pinch, kick, curse, spit. They let him watch terrible things on YouTube. He beats the animals. My dad and sister egg him on and think it's funny. He takes things from Haley(my daughter) or will hit her with a toy and they don't tel him no. There was one time he threw a hard toy at her and she was crying and I asked him to say sorry and he said no. Then I got her calmed down and asleep and he came over and kicked her bouncy and woke her up. I told him stop and he spit at me, I told him if he does it again I would put him in time out. He did again and when I put him in time out my mom and sister both told me not to and he's fine. Seriously? My sister does nothing and in return gets my mom as a 24/7 baby sitter but I do EVERYTHING in terms of raising my daughter and the second I need help I don't get any because my mom either has him or is finally free and doesn't want to help. There are times I ask for my mom to watch my daughter to run errands (any time I go out it's for my daughter, never just to go out with friends or have fun) and my mom will tell me know because she's with my nephew WHILE my sister AND her bf are home, they just don't watch him. I need a break, it pisses me off that my sister does nothing for her son and has a 24/7 break. I literally have to cut 5-6 hours of my sleep every night in order to get anything done such as showering, laundry, cleaning, bottles etc. and my sister lets her son wake my daughter up so she's up till 2am and I don't go to bed until 6-7am, and run off of 3-4 hours of sleep a day; but she gets all the sleep and naps in the world. It's harder on me too since I'm the responsible one and I'm older (21) I'm expected to not need a baby sitter or a break. I get excuses, complaints, ignorance and eye rolls when I ask for someone to watch her it's sick. There are 12 people in this house. It's sad because my moms excuse is "well if I don't do it, she's not going to and he's on his own. At least he has us (her and his aunts) to care for him. His parents don't." She also told my mom she doesn't want to go to college or do anything with her life. I forgot to add he didn't come out with being pregnant until she was 32 weeks pregnant, she was tiny her whole pregnancy and didn't say anything until we found the tests and my mom asked her ourselves, and even then still tried to lie. My sister is also a terribly compulsive liar. I don't want my daughter to be around all these people daily, she's going to be raised a way I don't want her to be. Sorry I really just had to vent.