This series comprises correspondence sent to other members of the Trevelyan and Philips families but which was held alongside Charles and family's papers. The sub-series are as follows:
- CPT/5/1 - Letters to George Otto and Caroline Trevelyan nee Philips from and about Charles and family
- CPT/5/2 - Letters to George Otto and Caroline Trevelyan nee Philips from various correspondents
- CPT/5/3 - Letters to Robert Calverley Trevelyan from Charles
- CPT/5/4 - Letters to various Trevelyan family members and related papers
Further correspondence with George Otto and Caroline Trevelyan can be found in this collection at CPT/1/9 and CPT/2/8.