Hi Christiaan,
You can use the following method:
public XPath<T> eq(Object... pathAndValue)
In your example this becomes something like the following:
XPath<ProcessElement> xpath = XPath.create(getContext(), ProcessElement.class);
xpath.eq(
ProcessElement.MemberNames.ProcessConnector_ProcessElement_Parent,
ProcessConnector.entityName,
ProcessConnector.MemberNames.ProcessConnector_ProcessElement_Child,
childGuid
);