In Fahrenheit 451, Montag's wife Mildred considers the characters on the three TV walls that surround her her family. Montag thinks, "Well, wasn't there a wall between him and Mildred...And the uncles, the aunts, the cousins, the nieces, the nephews, that lived in those walls, the gibbering pack of tree apes that said nothing...He had taken to calling them relatives from the very first" (page 44 in the Del Ray Edition, 1991). In other words, the characters on the wall present a literal and metaphorical wall between Montag and Mildred.
The characters on the wall speak to Mildred, and she is always engrossed in their drama so that she pays very little attention to Montag or to the world around her. Montag thinks of his wife as "a little girl in a forest without trees" (page 44), which conveys that Mildred is very lost and disconnected from Montag. She lives her life watching TV, taking sleeping pills, or listening to music through inserts that look like seashells in her ears. Her intention, encouraged by the government and society around her, is to drown out reality so that she does not pay attention to anything real, only to her fictional relatives on the television screens.
Mildred Montag considers the characters on television to be her family. She watches tv on her floor to ceiling three tv screens and the shows allows her to interact with the actors.
All she does is sit around and watch television all day.
They are who she considers to be a family, which are the characters in the television.
Mildred's Family is the characters that she watches on her TV.