We can't predict the future nor can we rewrite our estate plans every time anything happens at all in our lives that could affect a decision in our plan. It is important that estate plans prepare for the unknown through careful drafting and alternative terms. It is also why you should not only have an attorney to help, but carefully select one who is experienced in drafting wills, trusts and other instruments.
There are many situations in which errors in a will have resulted in unintended consequences. For instance, let us look at an example in which a grandfather set up a will providing for his grandchildren by leaving a large portion of his estate to them.
In this situation, the grandfather wanted to leave much of his estate to his grandchildren, the intended beneficiaries. As with many grandparents, he set up a graduated schedule for the inheritance, allowing the children to access the funds for college at the age of 18. Then, the children would have access to more at 21, 25 and then again when they turned 30.
It is a very typical plan, the only problem was that the grandfather's will failed to include the grandchildren who were not yet born at the time when he drafted the will. Thus, the children who were later born were excluded from the will. The parents reported that the grandfather did not and would not have intended this result. The problem was that the law didn't leave much room for altering the plan after the fact.
Follow the advice given in the beginning of this post if you are concerned about whether your plans are adequate for your goals.
Source: The Washington Post, "Inheritance, co-signing -- frank advice for readers," Michelle Singletary, Oct. 21, 2014