My mom was widowed and I was an only child, we lived in a 900 square foot house – it was perfect for us.
I really liked my San Diego house, it felt spacious with 1600 sq ft – 3 bed/2 bath. The only issue is that my son has asperger’s (mild autism) and has trouble keeping his modulating his voice (he get very loud), so it can be difficult to get away from the noise. Otherwise I think 1600 sq ft is great for a family of 4.