Carolina Herrera pushes a stroller through the slushy city streets, propelling one-year-old Zavier, as well as her own two-year-old daughter, Mariana. Herrera is small, and the double stroller takes a lot of her strength—usually, it’s a single stroller, and Mariana is at home with a neighbor while Herrera’s partner, Marco, works long hours as a construction worker. Zavier’s four-year-old brother Toren walks alongside them. Herrera implores the kids to put on their tiny gloves: it’s…