Question on small business partnership/ ownership

Question on small business partnership, 3 of us start a small business(investment company), friend A put in a little more than $12,000, and friend B put in $10,000 and they initiate and plan the company about 4 months and then invite me "C" to join as technologist person and I put in $20,000, “A” expertise is business operation so he is the brain of the company and want to be the CEO, “B” the other co-founder will be the assistant, I mainly be the technical person(web design, etc). Currently the other two friends still working as full time employee on their regular job and work part time for the company after hours, because my work require full time bases, so I quit my regular full time job to start to work and I in the mean time convert my parents garage and start working full time. We hold our regular business meeting at my parent’s garage twice a week. I receive about $1000 a month as salary which is below market value as technologist while the other two do not receive any income and any profit that the company generates is reinvest into the company.
My question is under the situation that I describe above, even I invest the most into this company but my expertise is technologist and do not want to be the CEO, but how much percentage of the company should I own is fair and if “A” want to be the CEO , how much share should each of us own, currently it is A = 65%, B=20%, me the C=15%, is it fair? If not, how should we divide the share of this company, can this be change even it is already on a legal document, we welcome any advice on this. Thanks in advance.