I have had relationship with some family business and I just found more disavantages than advantages in there.
If you want your family business takes off you have to separete business of personals issues. When most a family is involved, this is almost impossible because can exist huge problems that affect the increasing of the business. Also, it very importat to understand that incomes or utilities obteined should be to invest them on the business. It is very common that members of the family put their hands to take money of the business to personal expesens affecting the activities or its evolution.
Another very common desventage is where we called "juniors" in my place. Frecuently the children take an important roll in the family business, many time with no knowledge. So, they just affect the business with their wrong decisions, their bad actitude, their inefficient job, etc. However, all that doen't mean everything is negative, there are many family business that have taken off with a good organization between the members of the family involved. I think if you open a family business you have to stablish rules, mutual objetives, assigning agreed work and if it is possible, formalize the relationship with contracts.