@Felicia268
As @Mike-And-Jane0 mentioned, instant book is not the issue. If you manually block dates on a calendar for personal use or direct bookings, you MUST block those dates manually on ALL the listings. Only actual guest reservations on Airbnb will block all the calendars and prevent double bookings.
This is intentional, as some Hosts block the smaller "child" listings during high season and on weekends in hopes the larger listing gets booked first. Once the larger listing is booked, you can manually unblock the smaller ones.
Link Listings Correctly
for 3 listings with a large, all inclusive "Parent" and 2 smaller "child Listings:
Link Child A to parent
Link Child B to parent
Don't try to link the Parent to the children. I'm not sure about but if someone books child B, child A should still be able to be booked; its a separate listing, but it should block the parent.
So for a 3 bedroom house, you have a parent listing with 3 bedrooms. Then you have a child A listing for one bedroom, and a child B listing for one bedroom. However, if you have a listing that combines 2 bedrooms together, that would be a child C and not sure how that would need to be linked to prevent Child A and Child B from being booked?
Ok....now I'm really confused.
Maybe another Host can chime in here who has actually done this?