They told us the free breakfast offer we booked was only for two people per room, so we had to pay for breakfast for the third person. Can anyone confirm if this is correct, because I can't find any info online.

Always 2

Just back and can confirm 2 per room Still a pleasant stay

Usually offer is for a two person room....

Yes, offer and special rates are mostly limited to two persons pero room

Third and fourth guests are not included in those promotion unless specifically noted. It is always good to ask at the time of booking to the hotel directly.