Let's talk about value. There are three types of value, in my mind: wisdom value, cash value, and potential value.
The cash value of this experience is your salary. You don't seem happy with it.
The wisdom value of this experience is hopefully clear: Take ownership, have things written down on paper, and don't do work for free. Also, another nugget of wisdom: Many people here on HN have been screwed in situations where they thought they were getting equity and they weren't - the difference is you lost it to family. This is actually not that bad. I'll explain later. The main point is to not make the mistake of doing free work for no equity again.
The potential value is pretty much zero. You're not going to get much more from this company, at least compared to the opportunity cost of working for a different startup that values you or starting your own. You've fooled yourself that there is potential because "you started it" and "you deserve it." but there isn't and you're screwed. Accept it.
From the little information I have, I think your next best action is clear: move on, do something new. Start a new company, you clearly have the chops and the experience. You have a distinct advantage over most people starting companies because your family is also made up of business people. (I know I know - your hear is sinking - but stay focused on being rational.) But this makes you incredibly lucky.
Lets say you move on - work for a new company - start your own - whatever. You live life. In 10 years you're married and you have a baby. Your parents are getting old and the company now has a lot of liquid assets and everyone is super comfortable. Your parents now buy you a house, or set up a trust for your kid to go to college. Very few people have this. You, again, become incredibly lucky. Your brother, too, will get these benefits. What luck! What a wonderful life all the cousins will have.
There is an African folk story about a man who fell from a very tall tree onto a medium size tree, and then from a medium size tree on to the ground. He was all scratched up, but he survived because of the interim tree. An elder looked at him scowling and reminded him, "don't ask god why, when you should tell him thank you!"
You made your family rich. You achieved IT, and I hope one day after the rawness of the emotions fades, you can feel pride about this entire experience. Your parents did not do the right thing - but thats okay, few people do. Maybe one day they will. But it is THEIR choice - the ball is in their court. These choices are difficult. Thankfully, it's not your choice! Forgive, learn, move on, and be thankful!