D.C. Code § 21-149: Parties.

The infant, together with those who would succeed to the estate if he were dead, shall be made parties defendant in the proceeding provided by section 21-148 ; and the court shall appoint a fit and disinterested person to be guardian ad litem for the infant, who shall answer the petition under oath. The infant also, if above the age of 14 years, shall answer the petition in proper person, under oath.