About protestant christians/churches in kerala??

Malayali protestant christians have often been known to have a different tradition or doctrine of faith as compared to the Catholics and Orthodox in kerala.

Despite this I have seen that Orthodox and groups are more closer to the protestant groups like CSI, Marthoma with regards to matrimony and family than with Catholics. I have seen that even now, Orthodox and Catholic(both RC and LC) marriages are seen as a taboo by both the Orthodox and Catholic family groups despite having so much similar faith values. In online forums too, generally malayali Orthodox and Catholics always get along pretty well and often brand themselves together with regards to many similar faith values but in the physical world, the ground reality is different with malayali Orthodox and Protestants being more closer in terms of family/matrimony. What are your general thoughts on the same and does this vary between the various other protestant groups in kerala as some protestant groups like Pentecost who are seen as extreme by most of the christian groups when compared to the other malayali protestant groups.