This seems to be an absolute epidemic across the state. Same with condos. It's like they assume that apartments of any kind are only for single people and maybe a couple with one child. In other words, people who are dragging the fertility rate down toward 50%.
When I pull up Zillow and look at rentals across a huge swath of the East Bay, there are 8,309 apartments listed (I filtered out houses and townhomes). I add one filter: 3+ bedrooms. The number drops to 784. Fewer than 10% (!) of apartments listed have 3+ bedrooms. (Also, a quick spot check of these seems to show a nontrivial amount that are actually just houses with faulty metadata.)
This puts a tremendous burden on low-income people, to have to foot the higher cost of maintaining a home and/or of an absurd commute, just in order to have enough space[1] to have more than one kid. That, or overpay to compete for one of the few bigger apartments, many of which are "luxury" oriented.
Meanwhile, the high-income can afford a house or a luxury 3br apartment, but they are mostly high-income because they've deprioritized family, putting in 10+ years of being DINKs. In my circle of upper middle class tech types, many of them are 35-38 before having their first kid. 1 kid is much more likely than 3 for people starting in their late 30s, so this drags down fertility rates even among the "high income" subgroup!
[1] I know opinions vary on whether it's good and healthy to have kids sharing rooms, though imho I don't want a son and daughter forced to bunk together as they get older, and calls to 'just share rooms' is giving "Own nothing and be happy."
My parents raised eleven children in a typical four-bedroom suburban tract house.
I wonder why modern people would be different?
Much worse than housing is the vehicle when you cross the 5 or 6 kid boundary, your available vehicles begin to rapidly plummet.
Rent is a common complaint, but consider the costs of childcare, needing two incomes to stay afloat, etc.