Who said you were brainwashed?
I meet your criteria. I found God all on my own with no socialization of my parents. And no peer pressure or suggestions from anyone else.
By the time I was 20 I was missing something in my life. I went to a secluded section of a local park and contemplated and ask for guidance.
Over the next several weeks different groups came to my door to give me " the word of God" I sent them all away to see who would return. Only two returned. One was an old man that insisted Jews were the root of all evil and the other was the missionaries of the Church of Jesus Christ of Latter Day Saints. I decided to listen to the Missionaries. I already had a pretty good idea how the Catholic Church and Baptist Churches worked from history lessons in school.
Let me be clear, before I contemplated I had lived in my Grandparents house for several years and no religious groups had come to the door. Now obviously this could be coincidence but I do not believe so.
After months of lessons and talks and attending the VERY local church I had no problem seeing that the Church Of Jesus Christ of Latter Day Saints was where I belonged.
Shortly after officially joining the Church I went to Marine Corps Boot Camp. On Sundays in Boot Camp you are nearly forced to go to church , and the Drill Instructors prefer everyone go at the same time to the same place, a nondenominational service. 4 of us in My Company refused to go because there were separate Latter Day Saint services by an Elder of the Church ( the Government does not recognize Elders of the Church as Chaplins because they do not get degrees as such) We went a half hour after everyone else to our own services, which ate up most of the Sunday Morning 4 hours we had, it was lots of fun trying to wash our cloths and be berated by the Drill Instructors for not going to their services. Especially when we were in that first phase of Boot Camp, since third phase had first dibs on the wash racks so we had to wash after church.
Ask GunnyL how Drill Instructors feel when recruits do not conform to THEIR schedule. Every Sunday was the same, The Drill Instructor came in to the Squad Bay and announced we were going to church and to form up outside. I was the only one in my platoon that did not go, which entailed being brow beat and threatened by the Drill Instructor while I reminded him my services were a half hour later. I am sure the other 3 recruits in the other platoons went through the same ritual. We did this in first and third phase ( 2nd phase we were at Pendleton on the range or in the field, No services were given there.)