Barnes and Co was formed to control businesses in Warwick, Allora, Yangan and Roma Street and Commonwealth Flour Mills at Warwick and South Brisbane.

[3] He married Mary Cecilia Merry (ca.1858 – 3 October 1942) of Bulimba, Queensland in 1879.

A son, Franklin George Barnes (ca.1883 – ) was a mining engineer who devised and patented a method for degaussing British ships to counter the threat of magnetic mines in the early days of World War II.

G. P. Barnes felt his son's failure acutely, and personally paid out the company's preference shareholders.

[6] The former Barnes and Co. Trading Place in Warwick is listed on the Queensland Heritage Register.