Is it normal that my family grosses me out?

That's pretty obsessive and gross. Tell them to replace the toilets in the house with eco-friendly models that use less water when you flush. But showering no more than 1x/week is just unacceptable. My mom did that when I was a kid. I had to tell her that she stunk to high heaven. Since then she started showering daily. Maybe you should just say something.

Showering twice a day is excessive, but once a week isn't nearly sufficient, so you are the closest to normal here.

Oh man... That's really nasty.
It does sound like you might be a little excessive with your constant showering, but considering what you have to live with I don't blame you for wanting to be clean. Just be careful not to let it turn into a complex.
There's a difference between saving water and being a slob. It sounds like a flimsy excuse to justify what they're doing.
Good luck to you and... yeah, don't let them touch your stuff.

People that don't wash their hands after using the bathroom my disgusting!

Pretty gross, if you ask me.

it happens, my brother pisses in the sink and my mom doesn't close the door when she goes to the bathroom or flush; I understand where your coming from

Your family is your family. Gross, normal, clean, whatever, you don't need to worry about what they are - you need to worry about making your relationship with them work despite your differences.
I think both your family AND your reaction to them is normal. I have Obsessive Compulsive Disorder (diagnosed by a psychiatrist and everything), so I can definitely relate to being disgusted by other people - yes, even my family. What works for me is to remind myself that my dad doesn't wash his hands after he pees, but he did feed me and change my diapers and patch up my scraped knees. My mom hugs everybody at her church and then tries to hug me (GERMS!), but she did grow me inside of her body and push me out of her special place. It's almost like I remind myself they they have 'earned' their right to be germy, or that my love for them outweighs my disgust for their filth.
When it's just TOO MUCH, which it sounds like it is for you, I use very gentle language to kind of remind them that I have different views of cleanliness than them and to please respect that. "Dad, I know your hands aren't really dirty, but I would appreciate it if you'd wash your hands before we share the popcorn bowl, just to make me feel better."
Even if you don't think you're the problem, phrasing it that way makes it go down easier for them, and therefore makes them more likely to listen to you.
Good luck!

My family were the same in the 60`s, then people only bathed once or twice a week, & hardly ever washed their hands. Totally gross, but the strange thing is that people didn`t seem to get so many illnesses as they do now, like norovirus & swine flu.

In my opinion, you seem to be the only one that is normal here...the examples you state are disgusting...while I haven't had to deal with most of what you have, I have had several people living in the same places that I do that don't want to flush the toilet frequently due to extra water costs. Cutting down shower times I understand to a degree, but that one is simply disgusting.

Looks like you are the only hygenetic, civilized person in your family.
They're just gross