Working for family...and it's not going well. (Long)

My grandmother owned a business for many many years that ended up going under when the economy collapsed around 2007. She is very knowledgeable about the industry and a great business woman.

She recently got the opportunity to open another business very similar to the old one, but on a much larger scale, and asked me to work for her. I am now working for my grandma and my aunt at their furniture store.

I went into this with the understanding that, in the beginning, they wouldn't have the profits to pay me. So I'm keeping track of my hours and they will be back-paying me once we start turning a profit. I agreed to that and I know she's good for the money. So that is NOT the main issue.

The big problem I'm having is the lack of trust, communication, and organization. We don't have a schedule. I'm lucky to get ~16 hours a week. I haven't been trained on ANYTHING. The only things I know are the things I've figured out on my own time. My aunt (who co-owns this with my grandma) will call me at 11:30 pm to ask me to come in the next day. I don't even get a 12 hour notice.

Also, they've completely left me out of the loop. Just the other day, they had a big training where one of our manufacturers came in and taught everyone about our customizable sofas. I wasn't invited. But my 16 year old cousin was.

A Master Florist did a training on our artificial flower arangments, which is supposed to be MY department. Again, I wasn't invited. But my 16 year old cousin was.

Our new computer system is being installed TODAY. The engineer is there teaching everyone how to use it. I was not invited.

I'm working for free, being treated like garbage, and expected to know things even though I'm not being trained.

Our Grand Opening is in a week and I need to have this worked out before then because I can't keep doing it this way. I'm frustrated, my feelings are hurt, and I could easily find something better. But this is my family. I'm so lost.

**Note: As far as I am concerned, I haven't done anything wrong to cause this. I show up on time. I take initiative. I'm willing to do the grunt work (I climbed into the dumpster the other day to find something because nobody else was willing to get their hands dirty). I work my ass off. I'm respectful. But I honestly feel like I'm being punished for something.

What should I do? How do I fix this?