According to Census ACS data, the % of all Minneapolis households with 3 or more kids is about 6-7%. Metro-wide, only 9.2% of all households have 3+ kids. Of family households with children, 3+ kids in the house is 28% in both Minneapolis and MSP. Catering to a very small household demographic, one that is extremely likely to continue declining as time moves on (as LakeCharles notes), shouldn't be a priority policy goal. Even if it were, massive single family homes in prime real estate a mile or two from downtown shouldn't be the means of achieving it, since 3 BR apartments, 3 BR units in triplexes, 3 BR townhomes, or other solutions can be had by redevelopment/subdivision. As a personal anecdote, I am constantly reminding myself how much unused space my 1,600 sqft home (plus unfinished but furnished basement) has, even with with a kid and 2 golden retrievers. There are just so, so many houses in Minneapolis proper that could fit a good chunk of the metro's family households if the old retired or young childless people would make more rational decisions about the square footage they actually needed. On my block alone there are 6 houses with a one or two 60+ year old people living in them that could have sold at a profit long ago and downsized to a 600 sqft apartment. How many newly-married couples buy a 3BR home without kids, then upgrade to the 4-5BR place one suburb out once they have a kid or two? Ignoring historic preservation goals, there really is no "need" for a single detached SFR in the Wedge today given how many SFRs there are across the city.
And, I'll also toss in again that the presence of *other* large, grand single family homes in a block is a fairly insignificant driver of property values for an individual grand, beautiful single family home. Barring the "Up House" nightmare, many people would love to live in a 3,500 square foot home on a quarter acre in the middle of an extremely walkable neighborhood. Unfortunately for affordability, there are more than enough doctors married to lawyers with one or two kids who can afford such a living arrangement at $500,000 or more bucks. If you're making a case that there are large households of immigrant or low-income communities with multiple generations or lots of combined kids that can pool together enough money to afford a big home, I'm with you - this is a thing and may be a better option for some families than breaking out into individual housing units. But we all know that's not what's going on in the Wedge or East Isles/LH.
Finally, I couldn't write a post this long without again stating that a terribly-maintained 100-year old house (by landlord or owner) isn't necessarily a bad thing. We need to ensure there aren't health/safety violations with this depreciation, but what other durable goods in our society are able to run their course that long? Of all the wasteful, consumerist, landfill-filling things we do in this country, I just don't think tearing down a house every 100 years registers on the scale.
Sure, it can be done, but how many families really want to do that if they can afford something bigger? That's my point. Those big houses are extra expensive because people want them and supply is limited in the area.
I'm just continually shocked you make this argument. There are actually families that live in apartments today with 1-2 kids and 2 BRs. In CARAG and the Wedge, they're more likely to be people of color and with lower incomes than the owners of large single family homes. They're able to afford living in those apartments today in an awesome location because some evil developers knocked down precious single family homes in the 60s and 70s. Why should we continue to accommodate a very small proportion of the population (very rich families with 3+ kids) over what we know to be a long-term place for middle/low-income families in the long-run?