no child under 14 can leave a will - there may be a decree for underage children if they had some entitlement that now needed to be be given to others. 14 was minimum age for marriage but very rare for Manx to marry under 21 (at which age many women seemed to rush to the altar)
Legacies might be paid years after the death as money became available - some testators would state money not to be paid until 21 but 14 was lawful age to have some control of finances though usually a guardian would be appointed (at 14 the child could choose their guardian)