If a person wasn't repentant when they got baptized/confirmed/received the Eucharist, are they a valid Catholic?

If a person wasn't repentant (sorry for their sins and living sinfully still) when they got baptized/confirmed/received the Eucharist in a cathedral but later on they repent (feel sorry for their sins) do all they have to do now is go to confession? Are they a valid catholic? Can you cite some sources too if you can please. Thanks.