I was brought up as an only child and hated it, I was very lonely sometimes. I had a friend who was the middle one of nine children. I loved visiting their home, it was noisy, chaotic, very 'lived in', and at mealtimes there was always room for one more! They were most definitely not wealthy but that was compensated for by an abundance of love. It was the sort of family life I wanted to have some day.
In the late 70s we had 3 children and soon discovered that this was considered to be a 'big' family. Entry to children's activities etc was always for 2 adults and 2 children. Many people (especially our parents) thought we were crazy. I didn't tell them I'd quite like a couple more! However, we reluctantly settled for three as we knew we could never afford to move to a much larger house. We had a wonderful family life with our children, and it's interesting that each of them now have 3 children.
I think these days 4 or more is probably considered a large family.