It depends mostly on two things: which cruise line you choose and when you sail. Family-focused lines during school holidays will have the most kids; adults-oriented lines during the school year will have the fewest.
By cruise line
- The most families: Disney, plus Royal Caribbean, Carnival and MSC, which are all built with families in mind.
- Fewer kids: Celebrity, Princess and Holland America draw more adults and couples.
- No kids at all: Virgin Voyages is adults-only, 18 and over.
By date
Even on a family-friendly line, the mix changes through the year:
- Most kids: summer break, spring break, Thanksgiving week, and the Christmas and New Year holidays.
- Fewest kids: while school is in session, especially September to early November, early December, and January to early March (outside holiday weeks).
- Longer cruises (10 nights or more) tend to have fewer families, since they're harder to fit around school.
What I do: I've always avoided holiday sailings, partly to skip the crowds, especially the kids, and partly because those weeks cost significantly more.
On board
Most family-friendly ships also have adults-only spaces, such as a quiet sun deck or adults-only pool, so you can find calmer corners even on a busy sailing.