"twin relationship" is correct and usable in written English.
You can use it when referring to the relationship between twins, especially when it is the focus of discussion or analysis. For example: "Recent research looks at the unique dynamics of a twin relationship, exploring the bond that exists between them."
You can't help feel that any Russian visitors would be so appalled by its state that the twin relationship would be ruined forever.
I began to spend less time writing articles about R&B singers and more time on poetry and stories, eventually starting work on a novel about the twin relationship.
According to Coventry's lord mayor Michael Hammon, Chinese investment in a new taxi factory outside the city was "more or less a direct consequence," of contacts made through the twin relationship with Jinan in eastern China.
Various ways of expressing the twin relationship in the cubic crystalline aggregates have been discussed.
Two variants possessing a twin relationship were found in the product.
Recrystallised grains with new orientations were also detected, these have a twin relationship to crystal orientations present in the deformation microstructure; the critically stressed slip planes being twin planes.
The twin relationships between the nanotwins were identified experimentally and theoretically.
The mobility of various interfaces, such as the twin boundary in a variant and intervariant interface is discussed, based on the identified twin relationships.
The Type-I and Type-II twin relationships were most prevalent in individual plate groups with low or high relative SEI contrast, respectively.
Martensite variants and twin relationships observed with EBSD after compressive or tensile deformation were determined to be consistent with those expected from calculated accommodation strains.
The twin relationships of the A C type non-modulated martensitic variant pair in Ni54Mn25Ga21 ferromagnetic shape memory alloy were investigated in detail through experimental observations and theoretical calculations.
