Section 128. Any minor resident in this commonwealth who shall have attained the age of fifteen years shall be deemed competent to contract for life or endowment insurance upon his life, for his own benefit or for the benefit of the husband, wife, children, father, mother, brother, sister or grandparent of such minor, and to exercise and enjoy every right, privilege and benefit provided by any life or endowment insurance contract on the life of such minor, subject to the foregoing limitations as to designation of beneficiary.