(1) Unless otherwise provided by the member pursuant to this act, the surviving spouse of a deceased member, deferred vested member, or retirant having the service qualifications required by section 23 shall be entitled to receive a survivor's retirement allowance for life payable from the survivors' retirement fund. The survivor's retirement allowance shall be payable beginning on the day after the date of death of the member or deferred vested member, or beginning in the month after the month of death in the case of a retirant. If an eligible child or children also survive the member, deferred vested member, or retirant, and the child or children are under the care of the eligible surviving spouse, the survivor's retirement allowance shall begin as of the day after the date of death of the member or deferred vested member or the month after the month of death in the case of a retirant, without regard to whether the surviving spouse has attained 55 years of age. The benefits to an eligible child or children shall continue whether or not the surviving spouse remarries. If the eligible child or children, or any of them, are not under the care of the eligible surviving spouse, at the specific designation of the deceased member, deferred vested member, or retirant as provided in this act, a survivor's retirement allowance shall begin for the benefit of the eligible child or children as of the day after the date of death of the member or deferred vested member, or beginning in the month after the month of death in the case of a retirant. A deduction from the monthly survivor's retirement allowance shall not be made for any fraction of a month remaining at the time of a survivor's death or becoming ineligible.

    (2) The survivor's retirement allowance shall be equal to 66-2/3% of the retirement allowance which the deceased member, deferred vested member, or retirant had earned on the date of death, as a member, deferred vested member, or retirant. If an eligible survivor, regardless of age, has in his or her care an eligible child or children of the deceased member, deferred vested member, or retirant, the survivor's retirement allowance shall be 75% of the retirement allowance, but when all the children have become ineligible, the survivor's retirement allowance shall be 66-2/3% of the retirement allowance.

    (3) An adopted child of a member for the purposes of this act shall have the same status as a natural child of a member.

    (4) If there is not a surviving spouse but an eligible child exists, or if an eligible child survives a surviving spouse, then the survivor's retirement allowance otherwise payable to the surviving spouse shall be paid in equal parts to each eligible child until the child becomes ineligible, and the total of the survivor's retirement allowance paid to any other child shall not be diminished because of the attainment of ineligible age, marriage, or death of an eligible child. The portion of the survivor's retirement allowance that was paid to a formerly eligible child who subsequently becomes ineligible shall be paid in equal parts among the remaining eligible children, if any, until no eligible children remain to be paid.

    (5) Marriage or attainment of ineligible age, whichever occurs first, shall render a child of a member, deferred vested member, or retirant ineligible for further consideration in the payment of a survivor's retirement allowance or in the increase in the amount of the survivor's retirement allowance under this act.

    (6) If the deceased member, deferred vested member, or retirant is survived by an eligible child or children who are not under the care of an eligible surviving spouse and if the deceased member, deferred vested member, or retirant has filed a written designation with the board, the survivor's retirement allowance or a part of it shall be paid to or for the benefit of the eligible child or children in the shares and in the manner as provided in the written designation. The deceased member, deferred vested member, or retirant may provide in the written designation that payment of all or any part of the survivor's retirement allowance to a surviving spouse not having the care of all of the eligible children shall be deferred until the children become ineligible.

    (7) If there is not a written designation by a member, deferred vested member, or retirant, and if the surviving spouse is not the biological parent of an eligible child or children, the survivor's retirement allowance shall be divided equally among the eligible survivors.

    (8) Unless designated by a member, deferred vested member, or retirant, when an eligible child or all of the eligible children become ineligible, the surviving spouse at the time of the member, deferred vested member, or retirant's death shall receive the entire survivor's retirement allowance.