Below is one of many examples of conflict arising from bad estate planning in a "blended" family (children from outside the marriage). The children almost lost their inheritance, and had to pay a big tax bill with penalties.
Blended families are very common these days and most of my clients in this situation are happy to learn of the various ways we have of preventing conflict through instruments that are more likely to implement the testamentary wishes of both spouses, as well as support the surviving spouse.
In Carl M. Upchurch et al. v. Commissioner; T.C. Memo. 2010-169; Nos. 14827-07, 14959-07 (1 Aug 2010), the Tax Court held that two estate beneficiaries were liable for taxes and interest on their bequests.