It’s not unusual to see people sleeping on the streets in the middle of the day. All Chinese seem to need an hour or so to sleep after lunch. However, this is the first time I have ever seen a small baby on a makeshift bed on his own on the street with no adult nearby. Perhaps they were working in the shop which was being ripped out.
The chances are that they are migrant workers with no support structure like grandparents in the city. Luckily Nanjing is a very safe city.