Rules on Civil Procedure
Section 13. Answer to third (fourth, etc.) - party complaint. - A third (fourth, etc.) - party defendant may allege in his answer his defenses, counterclaims or cross-claims, including such defenses that the third (fourth, etc.) - party plaintiff may have against the original plaintiff's claim. In proper cases, he may also assert a counterclaim against the original plaintiff in respect of the latter's claim against the third-party plaintiff. (n)