[2] The couple had a son and two daughters:[3] Ida and Horace Darwin settled in Cambridge, where they lived at "The Orchards", a 24-room mansion on Huntingdon Road.
Darwin was also on the committee of the Cambridge Charity Organisation Society and in 1908, in response to the recommendations of Royal Commission for the Care and Control of the Feeble-Minded, together with Florence Ada Keynes formed a sub-committee to enquire into the number of "defective" children in Borough schools.
The group campaigned for the passage of legislation that would put the recommendations of the Royal Commission into force and organised meetings and conferences.
In 1912 the Association, jointly with Cambridge University Eugenics Society, held a meeting in the Guildhall, where Ellen Pinsent read a paper on Mental Defect and its Social Dangers.
[8]Although Darwin reduced her public commitments following the death of her son in 1915, she maintained links with the Central Association for Mental Welfare until the end of her life.