Parent Left a Will
Generally, children are entitled to receive whatever their parent devises to them in a last will and testament. The only time a devise to children may be invalid is if the parent left more to her children than she was allowed to by law. For example, in community property states, marital assets are considered equally owned by both spouses. Thus, a surviving spouse is entitled to a certain portion of the marital estate; a deceased spouse cannot disinherit a spouse entirely or leave more than what she owned to her children in a will. If a parent left a will and left her child out, but did not explicitly disinherit her child, the child may have a right to an inheritance because it may be assumed the parent omitted her child by accident.
Parent Did Not Leave a Will
When a parent does not leave a will, she is said to have died "intestate." Children may have inheritance rights under certain circumstances if their parent dies without a will, particularly in states that are not community property states. In community property states, a surviving spouse is generally entitled to a deceased spouse's half of the estate -- and the half he already owns -- if the deceased spouse did not leave a will; this leaves the surviving spouse with 100 percent of the estate. However, a surviving spouse may not be entitled to the same amount in states that are not community property states -- known as common-law states. In these states, if a parent with one child did not make a will, but was married when she died, her surviving spouse may be entitled to at least half of the estate. However, if the deceased parent did not make a will and had more than one child, it is common for the surviving spouse to receive one-third of the estate; the other two-thirds typically pass to her children in equal shares.
A parent's estate may be probated whether she left a will or not. Probate courts help divide property according to a will or the inheritance laws of a particular state. If a parent left a will, and the will was admitted to a probate court, children typically have the right to demand an accounting of their parent's assets from the executor of the estate.
Children also have a right to contest a parent's will if they have valid legal grounds. For example, if a child was left out of a will and believes her parent's will is invalid because her parent was controlled by another person while making it -- or lacked the capacity to understand what she was doing while making it -- the child may contest the will in probate court. If the probate court is satisfied with a child's testimony, the court may grant an appropriate share of the parent's estate to the child.