@Kleanthis1
If you have 2 rooms to offer, then you can create a listing for each room.
You can also create a third listing for both rooms (to be in the search system also for 5 guests) and link them together (see Help files).
Then you can set the rigt pricing for each listing.
Now the couple booked both rooms for themself.
Additonal guests have to be booked from day 1 on the initial reservation. Otherwise they are considered as visitors, which useally (if allowed anyway in your houserules) wil not stay the night.
What the guest should have done technically is making 3 bookings: 1 week for themself, 1 week inlcuding the first couple and 1 week including the second couple.
It's too late now to make such changes.
Kind regards,
Emiel