Not long ago, when we talked about the "Manhattanization of San Francisco", we meant the increasing height and density of the buildings. We've moved past that -- given housing prices are higher in San Francisco by some measures. This causes a range of side-effects including, as discussed in a recent article in the New York Times, mixed-gendered siblings sharing bedrooms.
The article rightfully points out that not long ago, children didn't have their own bedrooms at all and instead slept where ever made the most sense... such as close to the warm fireplace. I would argue that the idea of everyone having their own room is a distinctly suburban one. When I was a child, my mother created an elaborate ruse because she decided one day it would be good for my sister and I to share room. This caused me to feel like I no longer had any room at all and didn't have a place in the house. Meanwhile a lovely large room stood empty right across the hall and, after many years, became part of the inlaw unit. I don't really understand it.
But the article touches on a bigger issue regarding raising a family in the city -- one of the barriers of entry and exit to/from the appropriate scale of housing for each stage of life. Some of my friends in San Francisco moved here after college and rented large apartments with their friends; the roommates dispersed and now those individuals have large rent-controlled apartments with their spouses and families.
But what about everyone else? There's a huge disincentive to leave a rent-controlled unit for a more appropriately-sized one -- you lose your low rent. Once you own, the transactions fees of correcting your housing investment can be prohibitive. Meanwhile emptynesters similarly have no incentive release their family-scale home back to the market in favor of a more manageably-sized one. All this causes a constipated market where housing prices are higher than they need to be because of unreleased of supply.
Siblings sharing rooms is probably a good thing regardless of gender. It forces young people to learn to get along with each other. It creates efficient use of space. And how luck are these kids to live in the cultural hubs of New York and San Francisco? They shouldn't be hanging out in their rooms anyway. But I wish it could be a more conscious parenting choice rather than one that is forced upon urban parents.