For example, assume this scenario: H & W have a child together, C. Shortly thereafter, W dies and H remarries W2 while C is still a young child. Together, H & W2 raise C and treat C as their own child, even though W2 never formally adopts C as her own child. Later in life, H dies and all of his assets pass to W2 as joint assets. C continues to care for and treat W2 as their mother. W2 then passes away without having executed a will. Who inherits W2's estate? Or, more importantly, who should inherit?
Under the intestacy laws, C would not inherit from W2 as there is no legal status of a parent-child relationship as required to inherit under the intestacy laws. However, over the past 80-some years, the Iowa courts, as well as 26 other states, have considered and adopted a theory called "equitable adoption", sometimes called "adoption by estoppel" or "virtual adoption" or "constructive adoption". Basically, a good summary of the theory stated by the Missouri Court of Appeals in Gardner v. Hancock:
An adoption by estoppel is an equitable remedy to protect the interests of a person who was supposed to have been adopted as a child but whose adoptive parents failed to undertake the legal steps necessary to formally accomplish the adoption; the doctrine is applied in an intestate estate to give effect to the intent of the decedent to adopt and provide for the child.In other words, the law won't punish a child for the mistake of the "parent" in failing to formally adopt the child through the legal system.
As the number of second marriages increase, in addition to "informal adoptions" and extended families as a result of cultural differences, as noted by Professor Higdon, and economic limitations, the argument of equitable adoption can be expected to increase in the court system.