The mixing angles of the CKM matrix which governs weak force flavor changing probabilities for quarks, and the PMNS matrix mixing angles which governs neutrino oscillation, show the following relationship empirically to the limited of current experimental precision:
This tends to imply that the the probability of a first to third generation transition in the PMNS matrix is a function of the probability of a first to second generation transition and the probability of a second to third generation transition, in the same way that it is in the CKM matrix.
This, in turn, suggests that the three mixing angles in each of the matrixes actually involve only two degrees of freedom (i.e. the three mixing angles are not fully independent of each other). If this were true, the number of mixing matrix parameters of the Standard Model would be six instead of eight.
This is also mathematically equivalent to the following:
In other neutrino physics, a new study claims to rule out (light) sterile neutrinos based upon cosmology data.