Am I Byzantine or Roman Catholic?

Recently, I found out that my grandfather was most likely a Byzantine Catholic. Plus maybe my father was raised in a Byzantine Church up north. However, I was raised in the south in a Roman Catholic all my life. So my brother telling me that I am Byzantine and so are my children; also he is telling that we must follow the Byzantine disciplines.
So I was initiated in the Roman Catholic thus am I Roman Catholic or Byzantine. If I am a Byzantine catholic than how do I convert? Do I have to officially declare my leaving of the Byzantine Church?

If (from 1983 or later) you are baptised at least age fourteen then you choose the sui iuris church, otherwise ascription falls to thesui iuris church of the Catholic parent or guardian: the father if he is an eastern Catholic, or the one chosen if there was an agreement between husband and wife. So the father and mother being older may have been under a different canon law at the time, however. It should be noted on your baptism certificate kept at the parish of baptism.

http://jimmyakin.com/2010/08/which-church-sui-iuris-do-you-enter-at-baptism.html

Thank you so much

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