Miles Beard's sister-in-law Mabel, his mother, his Grandma Beard, and his first niece:

Miles Beard's sister-in-law Mabel (married to his brother Max),
his mother, Bernice Griffith Beard,
and his grandmother, Sarah Catherine Hooker Beard.
The little girl is Miles' niece Mary Frances Beard, the daughter of Max and Mabel.
The child was born in February 1944; this was his first niece/nephew.
Miles taught the little girl to like mustard sandwiches.