Massachusetts General Laws
Article 3 - Representation
Section 304 - Representation by Person Having Substantially Identical Interest

Section 304. Representation by person having substantially identical interest
Unless otherwise represented, a minor, incapacitated or unborn individual or a person whose identity or location is unknown and not reasonably ascertainable, may be represented by and bound by another having a substantially identical interest with respect to the particular question or dispute, but only to the extent there is no conflict of interest between the representative and the person represented.