How can one tell if one needs to convert in order to be a Catholic or if one is already Catholic?
Would one's or one's ancestors' conversion to another religion or their lack of knowledge about Catholic change anything?
Christianity Stack Exchange is a question and answer site for committed Christians, experts in Christianity and those interested in learning more. It only takes a minute to sign up.Sign up to join this community
Unless one has been baptized into the Catholic Church or was previously validly baptized and then received into communion later, one is not Catholic. You cannot inherit it explicitly.
Thus, if you don't know already somehow, only people who knew you as a child might be able to tell you if you had been baptized and if so, by whom -- this is not an impossible situation although it's also not especially common.
How can one tell if one needs to convert in order to be Catholic or if one is already Catholic?
The answer is quite straightforward: ask your parents whether you were ever baptized in a Catholic church as an infant. The parish should have kept a baptism record. The diocese for that parish should have the record or at least help you to locate your baptism record.
If you find out you have been baptized, you can be practicing Catholic again by going to confession and receive communion regularly.
If there is no record of baptism, you can become a Catholic by participating in your parish's RCIA program which will prepare you for baptism, confirmation, and first communion.
If you are still not sure, including not knowing the parish where you might have been baptized, you can be conditionally baptized after going through RCIA.
Could one's Catholic status be obtained or lost by inheritance?
No. Being a Catholic is an individual decision, not inherited. If your parents or grandparents later converted to another religion or to become Catholic, their conversion doesn't affect your status at all.
Would one's lack of knowledge about Catholicism change the status?
If you have been baptized (maybe as an infant) you are a Catholic regardless whether you know about Catholicism or not. Ideally, your parents should have prepared you for confirmation & first communion when you reached the age of reason. But if that didn't happen, you are still a Catholic. If you don't go to church you are a lapsed / non-practicing Catholic.
Would one's conversion to another religion change anything?
What is clear is that you are no longer in full communion with the Church (see Canon Law 751). But it is possible you are still considered a Catholic. See the 2022 Catholic Answers article 'Once a Catholic, Always a Catholic'? by Jimmy Akin.