syntax = "proto3"; package examplecom; import "proto/othercom/external_child_message.proto"; message ParentMessageV3 { message InternalChildMessage { string my_string = 1; } InternalChildMessage internal_child_message = 1; repeated InternalChildMessage internal_children = 2; othercom.ExternalChildMessage external_child_message = 3; repeated othercom.ExternalChildMessage external_children = 4; }