158.—Subject to section 159, the increase payable under section 156(1) in respect of a qualified child who normally resides with the beneficiary and the spouse F949[, civil partner or cohabitant] of the beneficiary shall be payable at the rate of one-half of the appropriate amount in any case where the spouse F949[, civil partner or cohabitant] of the beneficiary is entitled to any benefit, assistance, allowance (other than supplementary welfare allowance) or any other pension under this Act.