Do Tamil Christians or Tamil Roman Catholics have a caste system?

I am a Tamil Hindu of Vellalar descent. Although I don't care about caste systems, my parents do. My boyfriend for 2 years is Roman Catholic and I don't know how to bring up this subject as its quite offensive. But what are the castes of Tamil Roman Catholics as I know the were originally Hindu before they converted to Catholicism or Christianity during the time Sri Lanka and India were ruled by different dynasties?