(1) Section 599 of the Principal Act is amended in subsection (1) by substituting the following for paragraph (a):

"(a) In this section 'child', in relation to a disposal for which relief is claimed under this section, includes -

(i) a nephew or a niece who has worked substantially on a full-time basis, for the period of 5 years ending with the disposal, in carrying on, or assisting in the carrying on of, the trade, business or profession concerned or the work of, or connected with, the office or employment concerned, and

(ii) an individual (in this paragraph referred to as 'the first-mentioned individual') who resided with, was under the care of and was maintained at the expense of the individual making the disposal throughout -

(I) a period of 5 years, or

(II) periods which together comprised at least 5 years,

before the first-mentioned individual attained the age of 18 years but only if such claim is not based on the uncorroborated testimony of one witness.".

(2) This section applies to disposals made on or after the date of the passing of this Act.