John Spooner Manning - 6 sons believed all killed in Boer War

The profile I merged with mentioned that John Spooner Manning had 6 sons, believed all killed in the Boer War.

From my grandfather's (John Spooner Manning b. 1940, current profile's great-grandson) writings (unsure of source if not family recollection):

"Grandpa [James Firmin Manning] had five brothers, being John Spooner (born 5/6/76 died 7/7/76), Frank (born 1878), William George (born 1/8/81), Frederick Reginald (born 1882), Walter George (born 1887) and one sister, Harriet (born 1870). ... Little is known about Granddad's brothers except that Frank established Lennox Pharmacy, the first in Johannesburg."

Elsewhere he writes that James Firmin Manning joined the Town Guard (Mostert's Redoubt) under Captain Mosely and "served with the Unit against the Boers, during the Siege of Kimberley (1899-1900)". However, he survived the war and met his future wife Johanna Wilhelmina Graaf (nee Voges) in 1902 when his unit was assigned to escort women and children back to their farms at the end of the war.