The present invention discloses a composition comprising at least one or more stereoisomers of a compound represented by the following Formula (1), wherein, in a gas chromatogram obtained by analyzing the composition by gas chromatography, the ratio of the area of the maximum peak with respect to the total area of peaks derived from the stereoisomers is 60% or more; and wherein the maximum peak is present within the range of retention time of from 27.6 to 28.0 minutes. The present invention also discloses: a curable composition comprising the above described composition, and one selected from the group consisting of a thermal cationic polymerization initiator, an acid anhydride-based curing agent and a curing accelerator, and a photo-cationic polymerization initiator; as well as a cured product therefrom. The above described curable composition is useful in that it allows for the production of a cured product having a high heat resistance. (In the Formula (1), R1 to R18 are each independently selected from the group consisting of a hydrogen atom, an alkyl group and an alkoxy group.)