My experience - internationally - generally yes free breakfast for 2 adults and 2 younger kids in the same room. But that was pre-covid and our kids were 10 and 5 (or younger). Since just before covid we book two rooms - have always gotten 2x people per room internationally.

Domestic US - I am booking 2 rooms x 4 people since the F&B credit went into effect. I would say it has been 50-50 -- some places giving me diamond elite + guest x both rooms, and others saying it is only for the primary room. When they say only 1 room we add my wife who has Gold to room #2 and that gives us Diamond x 2 and Gold x 2. If you are all in the same room pretty sure you are just getting the F&B x 2 people.