The analysis of the high resolution FTIR spectra and the diode laser spectra of the ν(E′)/2ν(A′ ⊕ E′) dyad of CNH, CNH and CNH is reported. The components of this dyad are found to form a system coupled by Fermi, l(-1, 2)- and l(2, 2)-resonances causing an 'infinite chain'. A truncated model of dimensions 6 × 6 including a virtual level was chosen accounting well for all perturbations. All assigned lines belong to ν and 2ν, respectively. No transitions of 2ν were detected. Some lines of 2ν were observed. But they are so heavily blended that assignments cannot be given with certainty. The upper state constants, the resonance parameters and the constants ω, χ, and g were derived from the fit of 4554 lines (CNH), 6626 lines (CNH) and 4671 lines (CNH). The results are summarized in the Tables 1-3.