Way too late for your project Ellie but I stumbled across this website and just *had* to reply to set some things straight. I have researched the Culpin family for years now since I'm also descended from a Culpin so I have gathered a large amount of information and pictures.
All the children and the wives you have fro George Francis Culpin are right (wife Kate Sherrington which he married in 1883 and had daughters Mabel, Edith, Norah, Margaret & Sarah and "wife" Florence Newman with which he had daughter Ivy, son Francis and daughter Verula. Florence became his wife officially in the 2d quarter of 1905 since Kate died 6 February 1905. He and Florence separated but never got divorced so he still left her his money when he died 1 May 1932).
But the doctor from the BBC series Millais Culpin wasn't his brother but his nephew.
George Francis' parents were Millice Culpin 1820-1888 & Sarah Squires Barrett 1823-1915. George had 11 siblings:
1- Millice Culpin 1846-1941 leather currier who enrolled as a student at London Hospital in 1877. He had married Hannah Munsey in 1869 qualified as a doctor in 1882 and emigrated to Australia in 1891 with his wife and 6 children. They settled in Taringa, Queensland were Millice ran a small private hospital he named 'Stevenage'. He was a rather stern looking man with a long beard.
His second child was Millais Culpin, 1874-1952 who married Ethel Maude Dimery Bennett on 19 April 1913 in Shanghai.
They had 1 daughter Frances Millais Culpin who was born in Australia. Millais was far more handsome than the actor who played him

I'll try to attach a photograph of him.
2 - Benjamin Ephraim Lamartine Culpin 1848-1928 married Eliza Matthews, had 7 children
3 - Catherine Culpin 1850-1932 married Francis Joshua Kirby & adopted Elsie Bertha Barrett Culpin
4 - Sarah Barrett Culpin 1851-1932 never married, became a nurse and later on Matron
5 - Eliza Anne Culpin 1853-1922 married Thomas Fraser
6 - Rachel Culpin 1854-1856
7 - Sophia Culpin 1856-1923 married James Roome, had 4 children
8 - Rachel Culpin 1858-1929 married Benjamin Kirby
9 - Charles Culpin 1859-? leather currier, married Clara Barrett, had 5 children
10 - stillborn male baby 1864
11 - Bertha Culpin 1866-1964, never married, 1st class clerk Custom House and General Postoffice
The parents of Millice Culpin 1820-1888 were Charles Culpin & Catherine Watts. Millice's eldest brother was called Charles as well and is my ancestor.
I have been able to find another 6 generations prior to Charles & Catherine and with all the children of every generation I have some very extensive branches in my tree. Do let me know if you would like to know more or get some pictures of either Millice (the 1846 one) or Millais.