A child born after a will has been executed by either parent or after the time in which a class gift made according to a trust arrangement expires.
The existence of an after-born child has significant legal ramifications upon gifts made under wills and trusts. Under the law of wills, the birth of an after-born child after the parent makes a will does not revoke it but has the effect of modifying its provisions. Generally, the after-born child must be given the share of the parent's estate that the child would have been entitled to if the parent had died without leaving a will, according to the law of descent and distribution. The beneficiaries of the will must contribute a proportionate share of what they inherited to make up the after-born child's share.
Under the law of trusts, a gift to a class is one in which the creator of the trust, the settlor, directs that the principal of the trust should be distributed to a specifically designated group of persons, such as to grandchildren, who are alive at a certain time, such as at the settlor's death. Any child born after this time would not be entitled to a proportionate share of the trust principal unless conceived before the settlor died. An after-born child born eleven months after the settlor's death, therefore, would not share in the principal, since the class had closed nine months after the settlor's death.
"After-Born Child." West's Encyclopedia of American Law. . Encyclopedia.com. (November 17, 2018). https://www.encyclopedia.com/law/encyclopedias-almanacs-transcripts-and-maps/after-born-child
"After-Born Child." West's Encyclopedia of American Law. . Retrieved November 17, 2018 from Encyclopedia.com: https://www.encyclopedia.com/law/encyclopedias-almanacs-transcripts-and-maps/after-born-child