Two years on, the third brother, Pearce Way, was a trooper in the New Zealand Rifle Brigade in the Ypres battle.
The advance started on 12 October 1917. Inadequate artillery support and churned up mud made the advance suicidal against the enemy defences.
Pierce fell some time during that day, and the assault eventually failed.
Included in the auction is a large range of other medals, many from New Zealand, and some awarded for great acts of bravery. The sale also includes a great range of other items including photo albums and documents, uniforms and equipment.
Auction manager Dunbar Sloane said the medals were expected to make $3000-4000.
They were previously part of a large "life time" military item collection.
There were about 300 military items to be auctioned this weekend.
The auction will be held at Auckland's Holy Trinity Cathedral Visitor Centre at 2pm.