Why are cousin marriage laws treated Unfair is there a need for UCC ?

I would like to get some understanding from the legal experts. Why is marriage with parallel first cousins not legal under HMA labeling it as Sapinda relation? I find this to be unfair as we see cross first cousins getting married which is legal under HMA & not Sapinda relation. Whether Cross or parallel first cousins both should be treated the same way. Such marriage laws have been interpreted in different ways and the rule itself has been subject to modification by local customs. Religion and north-south regional dichotomy in the culture largely determine consanguineous marriage to be legal or not legal. In south Indian Telugu Hindu culture marriage between cross-cousins is allowed and was the most preferred marriage for a very long time. ( Bava-Mardalu Marriage) whereas parallel cousin marriages are still taboo & only practiced in few areas of Karnataka & Tamil Nadu. The quite contrast is the North Indian Hindu culture where its strictly prohibited. Uniform civil code ?