Genealogy of “Jane Eyre”
The family tree below shows the characters in the novel who are related directly to Jane. The dates are based on my interpretation (see the timeline) but, even if they change, the relative relationships will remain.
We know that John Reed was fourteen at the beginning of the novel and Georgiana eleven. Eliza is older than her sister but we don't know if she was older than John.
There is a birthdate for St John Rivers but not for Diana and Mary. It is not possible then to work out the age relationships of the three (although Diana seems to be the elder, at least to her sister).