An American born and brought up in Europe in the 19th century, he is known as a painter of glamorous society, the first choice to show you had “arrived” in fashion and in status.
Many of his portraits however were of more modest subjects though always demonstrating his fascination with light & shade.
His great painting heroes included Velázquez, as can be seen so clearly in this group portrait.
It was certainly not a traditional depiction of children and quite unsettling in its atmosphere. See it next to Las Meninas below.
It’s even a similar scale as can be seen here displayed with the vases from the painting.
Please note that all images here are screenshots from Alex’s talk.