George your question led me to look at 2nd Class and it is different.
Only two seasons, with the East and Westbound Summer Seasons being the shorter than for 1st Class.
Eastbound: 2nd Class 1 May to 15 July [1st 1 May to 31 July]; with
Westbound: being 15 Aug to 30 Sept [1st Class 1 Aug to 15 Oct.
For the Winter Season 2 rates $65 per adult except for the 20 [18x4 & 2x2-berth] outside rooms on
D-deck where the rate was $67.50
Children of 1 year and under 12 half fare each. Infants under 12 months $7.50. The right is reserved to charge full fare for one child occupying a whole berth.
No Westbound tickets issued to children under 16 years unless accompanied by or coming to join parent or parents.
- {Note many of the 2-berth rooms had a Sofa in Room sufficiently large to accommodate one child.} - So presumably the full-fare rule would not apply.
For the Summer season the rates vary Eastbound to Westbound with a range of prices. the columns are headed:
For 4 adults each; with the other columns headed for 3 & a half, for 3, for 2 & a half, for 2 adults in a room.
So for: D-54 the 5 columns across read in US dollars
Eastbound: $72.50; $277.50; $265; $252.50 and $240
Westbound: $77.50; $297.50; $285; $272.50 and $260
This tells us that while berths could still be booked that in the Summer Season 2 or 3 passengers with or without a child could pay a premium and book a 4-berth room.
I hope that may be of interest.