In this paper, actuarial justification is explored in details for equal or unequal sharing of premiums and benefits between policyholders in a product involving joint lives. The analysis reveals a fundamental difference between endowment and assurance type of products in this regard. In assurance plans, there is a clear basis for differential structure in terms of sharing premium payment that is illustrated with examples. In pure endowment plans,the default system of equal premium for equal benefit may be more justified although implication of other alternatives are also considered. A justification is derived for such an alternative through an appropriate discount figures as compared to the individual live policies. An alternative actuarial principle is also suggested to deal with joint endowment plan and solutions have been worked out under this framework.