Massachusetts General Laws Part II. Real and Personal Property and Domestic Relations (Ch. 183-210) Ch. 185, § 26

First, Persons who claim, singly or collectively, to own the legal estate or easements or rights in land held and possessed in fee simple.

Second, Persons who claim, singly or collectively, to have the power of appointing or disposing of the legal estate or easements or rights in land held and possessed in fee simple.

Third, Infants and other persons under disability, by their legally appointed guardians; but the person in whose behalf the complaint is made shall be named as plaintiff.

Fourth, Corporations, by any officer duly authorized by a vote of the directors.

One or more tenants for a term of years, which is regarded as a fee simple in section one of chapter one hundred and eighty-six, shall not bring an action except jointly with those who claim the reversionary interest which makes up the fee simple at common law; nor shall a mortgagor, except as hereinafter provided, bring an action without the written consent of the mortgagee; nor shall one or more tenants bring an action who claim undivided shares less than a fee simple in the whole land described in the complaint for registration. If the holder of a mortgage does not consent to the complaint, it may be entered nevertheless, and the title registered, subject to the mortgage, which may be dealt with or foreclosed as if the land subject to it had not been registered. The judgment of registration in such case shall describe the mortgage, and shall state that it has not been registered and that registration is made subject to it, and shall provide that no subsequent certificate shall be issued and no further papers registered relative to such land after a foreclosure of such mortgage.