Clathrate hydrates of structure II with organic cyclic oxides were identified to have the ability to include molecular hydrogen into their empty small cages at near-ambient temperature and moderate pressure. Solid-state NMR and Raman spectroscopy of the included hydrogen molecules indicate that the small cavities are both singly and doubly occupied by hydrogen molecules in the mixed hydrates. The inclusion mechanism can be derived from the critical progression of the cage occupancies as determined from in-situ kinetic experiments on formation and decomposition. The inclusion ability of hydrogen molecules was observed for several organic clathrate hydrate formers such as THF (tetrahydrofuran) and 1,4-dioxane, suggesting this to be a general property. A structural transition of the simple amine hydrate was suggested to produce a novel double CH4 + t-BuNH2 hydrate as confirmed by using microscopic analytical methods. The corresponding hydrate compositions were determined by using NMR spectroscopy to describe a tuning mechanism to increase the storage capacity.