Quick response? Yes.
If you want to know whether it is at all possible for any human being to be ultimately admitted into Paradise without being baptized or being a member of any Church beforehand. I say yes it is possible. But if you are asking if someone who is raised Catholic or Christian can make heaven without adhering, to the best of their knowledge, to the faith they’ve been taught, then that’s another issues all-together.
Think of dead unbaptized infants for instance, it is unreasonable to hold that since they were not baptized before death, they will not make heaven or will be barred from the full enjoyment of heaven: the Beatific Vision. I personally believe that, since Christ has accomplished the task of objective Salvation, each person who is able to receive can now receive and be saved, if they reject, they will not be saved. But if one is unable to choose, has not been given the opportunity to, or does not even know about Christ, they too can be saved. In the case of the infants, they WILL BE SAVED by Christ who does not want any of his creatures to be far from him. This is because they have not committed any actual (personal) sins. God will definitely have a way to apply the sufferings of Christ to them and cleanse them from original sin. God is able to do unheard of things to bring salvation to man, he who is God came, took flesh and died. If you can understand that love and willingness to save us, you will understand why that love will not allow innocent babies to perish.
Also it is believed by the Church that those who live though life without knowing God or his Christ but have followed the dictates of Natural Law all though their lives will also be saved. Those too who have heard about Christ but are born in other religions and therefore do not share the conviction of the Christian Faith can be saved as well, as long as they follow the dictates of a morally upright conscience in their affairs.
What this generally means is that God has his way of bringing people to his kingdom who are innocently ignorant or who have not been given the opportunity to prove themselves in life. They too have a chance to be saved and their actions will be judged based on what they had or knew in life.