Hi @Rick3713
This is difficult to trouble-shoot without knowing your calendar availability settings for all 3 listings and not sure I'm totally clear on what is happening. @Mike-And-Jane0 are very knowledgable on this and might be able to advise better.
The multiple listing concept you have is a good one. The parent listing usually gets booked further out and the child listings are generally blocked by the Host for weekends and high season (parent more likely to get booked).
Airbnb looks at Reservations and Blocking as two different things when dealing with mulitple listing calendars for the same property. Reservations on the child listings will automatically block the parent listing. Reservations on the Parent lising will automatically block the child listings. However, if you want to block dates (not involving a reservation) you would have to do it on all the calendars involved. This is so Hosts can manually block the child listings when they want the parent to be booked (I think 🤔).
Here is what I can offer (without being able to see your listing calendar settings). Of course, be sure you have Instant Book (if using) turned OFF on all the listings while you try this. Not sure it will solve it and I might have this wrong:
Calendar Linking
Parent
Child 1 - Link to Parent
Child 2 - Link to Parent
Parent Listing
Leave your default availability as 12 months
Child Listings
Set your availability to "Unavailable by Default." Then go in on the child listings and manually unblock dates (you mentioned 90days).
Perhaps @Mike-And-Jane0 can correct this if I got it wrong?