java-tutorials/maven-modules/maven-parent-pom-resolution/maven-parent-pom-aggregator/parent-pom-module2/parent-pom-module3/pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <artifactId>parent-pom-module3</artifactId>
    <packaging>pom</packaging>

    <parent>
        <groupId>com.baeldung.maven-parent-pom-resolution</groupId>
        <artifactId>maven-parent-pom-aggregator</artifactId>
        <version>1.0.0-SNAPSHOT</version>
        <!-- removing relativePath won't work even if project-a is the aggregator project -->
        <!-- it only works in IntelliJ IDEA when project-a is registered as a Maven Project -->
        <relativePath>../../pom.xml</relativePath>
    </parent>

</project>