Feeling Unwelcome in a Shared Living Situation

Hey, so my significant other and I are having some troubles with our family situation. So we share 2 kids plus he has 2 older children that live upstairs with their mother and another brother. This is her house and all 8 of us are living together. We pay half of the mortgage and half electricity, as well as the whole internet bill, at least half the groceries and pitch in for things like garbage bags and paper plates and other like items. My s/o and I are the only ones with a car so we also have a dump sticker and are responsible for taking recycling and trash to the dump every week. So obviously life gets to be a lot at times, but for the most part we don't really feel welcome here with the nagging of things needing to be done. We talk about having conversations on who does what and when but it never gets accomplished. She seems to be the superior parent when it comes to the older children and doesn't take what we have to say into consideration most times. We feel one of the teenagers especially doesn't get punished properly for things like getting into trouble at school or the way he talks to any of the adults in the house. He also is very sneaky and all she does is have conversations with him that don't result into anything. We pretty much don't have any say in any punishments we feel are necessary for certain actions. He of course still seems to act the same way. She also works a lot and is hardly home and won't even tell us what is going on half the time, if the older kids are going to friends houses or hanging out in town. They are 15 and 14. I especially feel that they have too much freedom but she feels that if we don't let him mostly do these things he will rebel or be even more disrespectful which honestly I don't think is even possible. We obviously are having a hard time communicating but everyone is almost always too busy to talk or just don't seem to care. I am done feeling like we don't belong when this arrangement was partly her idea. I do understand that we may need to step up a bit on helping out with things like taking the trash to the dump every single week or doing dishes more than a couple times every other week. I will say it is much harder with a child under 1 and a 6 year old with ADHD too. I just don't feel we are treated like equals. Any insight or advice is appreciated, please and thank you.