Inny, I was going to recommend you buy a second towel :-) Seriously, I'd make a list of 5-10 very specific actions that really make you unhappy and then try to think of ways to solve them? For example, give the kids "choices" of what to help with or trade-offs? If they want something bought or to go somewhere special/expensive and you want to help them, give them a "price" they have to pay in assistance to you.

I would see if I could feel badly for the younger "siblings," that they are not being taught to take care of themselves -- rather than take it personally, that they are disrespectful to you. Do some bargaining, some outright communicating, "How about I make some chicken adobo while you two take out the trash and clean up some of these dishes? How does that sound?" that sort of thing.

My stepmother and I had troubles communicating and I remember our best times were when I was asking her about herself/her childhood experience. Maybe getting to know the younger teens better and what their life is actually like would help? It's good you remember how it was when you were a teen but their experience might not be similar? Talk to them a bit, let them know you, your likes and dislikes?

I had a girlfriend whose mother was ill so her father did all the cleaning and my girlfriend and her siblings nicknamed him "Shirley" and "teased" him a bit about the cleaning. Make your enjoyment of living in a clean, orderly environment a hallmark of "you" and as they get to know and like you and look around at the comfort of living in a clean, orderly place, they'll probably pitch in more readily to help. But not everyone sees cleanliness and order the same way, it can actually be a "threat" to some. All behavior is "learned" and obviously your bf's family/siblings and friends didn't learn the same things you did? You can teach them but it won't be instantaneous. If it's too hard for you, you probably should get your own place and ask your boyfriend to try adjusting to you and your ways instead of the other way around.