"To Dear Lily, X'mas 1915": Granddad George, middle brother Albert, Nana (Lily), older brother Jack. Probably Auntie Lou's kids scattered around.
Notes from Bill Brook: "... back r L to R my uncle tim, my unc. tom, my unc claude my dad was not in the photo but he was the oldest child. My g/uncle George Ullyatt (aka Cocky ) Brook, his brother John William Ullyatt Brook (my G/dad) G/ma Brook (Bartlett) Mary- Geo's daughter and John William Ullyatt aka (uncle Jonnie ) ( G/dads uncle ) .F/row L Dads sister Mollie and (bro ) Charles ..." IN CONTEXT, THE GIRL ON THE RIGHT IS GRANNIE, AND THE GIRL AT THE FRONT IS AUNTIE MOLLY. BEHIND MOLLY'S RIGHT SHOULDER IS MY GREAT-GRANDFATHER GEORGE ULLYAT BROOK