Legal background to trusts and estates: minor is entitled to income arising
If a beneficiary is entitled to receive the income arising, his interest is normally vested. But Section 31 Trustee Act 1925 affects the interest of an unmarried minor. The interest of an unmarried minor is reduced to being contingent.
Until vesting on marriage or otherwise, the trustees have discretion to use income arising for his benefit. Otherwise, it is accumulated.
Contrast this to the situation where the beneficiary is entitled to the whole of the income arising. The vested interest is not affected by the beneficiary being an unmarried minor because the effect of Section 31 is overridden by the reference to the whole of the income.