Since California is a community property state, most assets acquired during marriage are considered marital property to be divided in the case of a divorce. However, there are a few exceptions to this rule, including inheritances. To maintain an inheritance as separate, the beneficiary should not commingle that money with jointly owned assets.
If the inheritance is set up as a third party trust, it might be considered a marital asset. Therefore, unless the people who created the trust were specific about its uses, the beneficiary's former spouse could be entitled to half of the trust assets. This works two ways. A third party trust can also be created to support both people in a marriage. An example of this might be if parents have a child who is ill or has substance abuse issues. The parents may have a good relationship with the child's spouse, and they might want to ensure that this individual is also taken care of if the marriage dissolves.