see - sc.judiciary.gov.ph/jurisprudence/2013/april2013/178952.pdf
"x x x.
The Court’s disquisitions point favorably toward the direction of petitioners’ argument. In Heirs of Domingo Hernandez, Sr. v. Mingoa, Sr.,
38 the Court ruled that –
‘The general rule is that the certificate of non-forum shopping must be signed by all the plaintiffs in a case and the signature of only one of them is insufficient. However, the Court has also stressed that the rules on forum shopping were designed to promote and facilitate the orderly administration of justice and thus should not be interpreted with such absolute literalness as to subvert its own ultimate and legitimate objective. The rule of substantial compliance may be availed of with respect to the contents of the certification. This is because the requirement of strict compliance with the provisions regarding the certification of non-forum shopping merely underscores its mandatory nature in that the certification cannot be altogether dispensed with or its requirements completely disregarded. Thus, under justifiable circumstances, the Court has relaxed the rule requiring the submission of such certification considering that although it is obligatory, it is not jurisdictional.
In HLC Construction and Development Corporation v. Emily Homes Subdivision Homeowners Association, it was held that the signature of only one of the petitioners in the certification against forum shopping substantially complied with rules because all the petitioners share a common interest and invoke a common cause of action or defense.
The same leniency was applied by the Court in Cavile v. Heirs of Cavile, because the lone petitioner who executed the certification of non-forum shopping was a relative and co-owner of the other petitioners with whom he shares a common interest. x x x
x x x
In the instant case, petitioners share a common interest and defense inasmuch as they collectively claim a right not to be dispossessed of the subject lot by virtue of their and their deceased parents’ construction of a family home and occupation thereof for more than 10 years. The commonality of their stance to defend their alleged right over the controverted lot thus gave petitioners x x x authority to inform the Court of Appeals in behalf of the other petitioners that they have not commenced any action or claim involving the same issues in another court or tribunal, and that there is no other pending action or claim in another court or tribunal involving the same issues.’
Here, all the petitioners are immediate relatives who share a common
interest in the land sought to be reconveyed and a common cause of action
raising the same arguments in support thereof. There was sufficient basis,
therefore, for Domingo Hernandez, Jr. to speak for and in behalf of his copetitioners when he certified that they had not filed any action or claim in another court or tribunal involving the same issue. Thus, the Verification/Certification that Hernandez, Jr. executed constitutes substantial compliance under the Rules.39 x x x."
