Can an illegitimate adult child contest a will?

Yes, an illegitimate adult child can contest a will, depending on the laws of the jurisdiction. Many places recognize the rights of all children, regardless of their legitimacy, to challenge a will if they believe they have a valid claim, such as being improperly excluded or if they suspect undue influence or lack of testamentary capacity. However, the specifics can vary widely, so it's important for the individual to consult legal counsel to understand their rights and options.