Lydia Field Emmet (January 23, 1866-August 16, 1952) was an American artist
best known as a painter of portraits, particularly of children.
Biography on Wikipedia: https://en.wikipedia.org/wiki/Lydia_Field_Emmet

The Brothers by Lydia Field Emmet
1909 / Oil on canvas / 64 3/16″x47 5/16″ / Brooklyn Museum, NY, NY

Lydia Field Emmet on Artnet: http://www.artnet.com/artists/lydia-field-emmet/

Further reading:
http://www.schwarzgallery.com/artist/69/Lydia-Field-Emmet
http://arcadiasystems.org/academia/cassatt6c.html#emmet
https://www.nga.gov/collection/artist-info.1267.html?artobj_artistId=1267&pageNumber=1#biography