How many TOC can you nest?

I have 3 books, each with several chapters and their own TOC covering their own topics.

I place all 3 books into a parent book, also with its own TOC that covers all of the kids.

When I publish, the only TOC that is included is the one for the parent. All of the child content is present, except for the TOCs.

Is this an undocumented feature of Framemaker?  Is there a switch or process I can use to make sure that the TOCs, from the parent and the kids, all show up?

(I tried a mini-TOC, but that has to be added to each chapter rather than the whole book.)

Thanks.