Del. Fam. Ct. R. Civ. P. 14
(a) When respondent may bring in third party. When permitted by law, at any time after commencement of the action a responding party, as a third-party petitioner, may cause a summons and petition to be served upon a person not a party to the action who is or may be liable to the third-party petitioner for all or part of the petitioner's claim. The third-party petitioner need not obtain leave to make the service if the third-party petition is filed not later than 10 days after service of the original answer. Otherwise the third-party petitioner must obtain leave on motion upon notice to all parties to the action. The person served with the summons and third-party petition, hereinafter called the third-party respondent, shall make defenses to the third-party petitioner's claim as provided in Rule 12 and counterclaims against the third-party petitioner and cross-claims against other third-party respondents as provided in Rule 13. The third-party respondent may assert against the petitioner any defenses which the third-party petitioner has to the petitioner's claim. The third-party respondent may also assert any claim against the petitioner arising out of the transaction or occurrence that is the subject matter of the petitioner's claim against the third-party petitioner. The petitioner may assert any claim against the third-party respondent arising out of the transaction or occurrence that is the subject matter of the petitioner's claim against the third-party respondent, and the third-party respondent thereupon shall assert defenses as provided in Rule 12 and counterclaims and cross-claims as provided in Rule 13. Any party may move to strike the third-party claim, or for its severance or separate trial. A third-party respondent may proceed under this Rule against any person not a party to the action who is or may be liable to that party for all or part of the claim made in the action against the third- party respondent.
(b) When petitioner may bring in third party. When permitted by law, when a counterclaim is asserted against a petitioner, the petitioner may cause a third party to be brought in under the circumstances which under this Rule would entitle a respondent to do so.
Del. Fam. Ct. R. Civ. P. 14