When using just one kie.conf file for all services, it is not possible to define parent and child service in the same file. This is mainly the case when having an uberjar with all kie dependencies bundled in. In such case such kie.conf file is needed for service registry to work.

E.g. a user wants to add DMNAssemblerService to kie.conf,
org.kie.api.internal.assembler.KieAssemblers = +org.kie.dmn.core.assembler.DMNAssemblerService

In such case service discovery fails with an exception
java.lang.RuntimeException: Child services [org.kie.api.internal.assembler.KieAssemblers] have no parent

I have a proposed fix ready. Will create a PR with it and a reproducer.