4N.I.Where a beneficiary receives in respect of any persons as being, or as falling to be treated as, children of his family an amount of benefit which by reason of section 1 is not properly payable, but would have been properly payable according to the rates in force at the passing of this Act or at that of the Insurance Act of 1967, and he receives it for a period for which there are payable to him or anyone else in respect of those persons or any of them allowances under the Family Allowances Act at a rate which would not have been payable but for this Act, then the amount of benefit overpaid and not required to be repaid shall be treated as properly paid, but up to that amount any arrears of allowances payable under the Family Allowances Act for that period in respect of those persons shall be withheld.