Is it normal for a family to function like this?

I think my family is a bit... Weird.

First of all, there's my dad. He has a job, but doesn't have many hobbies. He drinks, smokes, and is lazy. He doesn't do anything other than watch TV, drink, smoke, and go to work. Rarely, he'll go for a walk with my mum.

Then there's my sister. She's quite motivated and pretty much the opposite of lazy. She has very good grades and just got a degree from university. She does lots of exercise and works out at the gym, and has a good job with decent pay. But, she can get angry quite easily and acts quite bossy towards others.

My mum, she's the nicest one in the family; probably the nicest person in the world. She does everything for this family and constantly rushes 'round for everyone else to make sure we're happy. She goes to work, cleans, cooks, tidies everyone's room, does all the shopping and pays the bills when they need paying. My dad uses her as a slave. If he wants something, she has to go out and fetch it. For example the other day, my dad came home from work and instructed my mum to go out and buy him some cough syrup. No please, no thank you. He talks to her like she's a piece of shit. He never helps out with anything around the house.

Then there's me. I don't spend THAT much time with my family to be honest, because all they seem to do at home is watch trash on the TV. I don't talk to my dad much because I hate his personality. He's arrogant, selfish and extremely lazy. I think he's a good man at heart but I just don't feel comfortable around him, but this doesn't really bother me. I exercise sometimes, and I'm very motivated and focused on my music producing and my band. I treat everyone with respect in my house, especially my mother. I would never even think of shouting at her, or instructing her to do anything, or even swearing at her or anything like that. She and I seem to get along better than anyone else in the family. I might not help out as much as I could around the house, but I show her how grateful I am for all she does and I hate to see her being treated like a slave by my dad and my sister. (My sister likes to shout and get bossy towards my mum, even if my mum is doing something for my sister like cooking her dinner or going out to buy her something from the shop that she needs. My sister is also hypocritical; she talks about my dad behind his back, about how annoying or selfish he's being (we all agree he's lazy and selfish and it's becoming a problem), but my sister herself is almost as bad as he is sometimes with the way she talks to my mother).

Then there's my dog. He's really- just kidding.

I should probably mention that my mum doesn't know how to say no to my dad. She lets him get away with murder sometimes and she complains about it all the time but she never puts her foot down and never will, and it doesn't look like anyone else is going to step in any time soon. Also, my dad has left my mum before a few times, one time for another woman, but every single time he came crawling back and my mum just let him straight back into the family.

Is this a normal family? Or is it the most fucked up family you've heard of in your life? Because I'm starting to think it's pretty fucked.