You want to know more about past lives. Why are we blocked from knowing them? How do some people remember or know about them?
If we've lived many lives, but do not remember them, it has to do with the level of consciousness that we are at. The effluvia, from many lifetimes, lodged in our subconscious minds, usually blocks our memory. In yogic traditions, it is called samskaras, past life incidents, which contain recordings of trauma. It's trauma we have endured and trauma that we have caused others.
There are methods of releasing that trauma from the subconscious mind, which gradually brings back our awareness and memory of previous lifetimes. At the same time, our emotions rise to higher levels and we gradually move towards higher levels of consciousness. We become better people.
Some people do some kind of past life regression, sometimes through hypnotic techniques, sometimes through Scientology auditing and processing, which brings back remembrance of previous lifetimes. Scientology claims not to use hypnotism in its auditing and processing.
Sometimes young children remember their previous lifetime, in which they suffered a traumatic death, until they grow up and forget. A person at a high enough level of consciousness, who doesn't have the chaotic effluvia of previous lifetimes, blocking their memory, will easily remember previous lifetimes. I know individuals, at a higher level of consciousness, which enables them not only to remember their previous lifetimes, but also the previous lifetimes of others.
I am an unusual case. You can't go by me. I'm not an enlightened Guru, who remembers my previous lifetimes. I have one semi-awake dream or vision, which seemed to indicate how I died in my previous lifetime. I feel there wasn't too much trauma involved, because I was able to accept that death, without too much pain or negative emotion. In that dream, a young, well dressed man entered his office of work and was immediately shot through the throat by a coworker. After staring at his co-worker for several seconds, he turns to walk away and is finished off by a shotgun blast, from another coworker.
From what a psychic friend had told me of my previous lifetime and peculiar circumstances in my life, I concluded that's how I died in my previous lifetime, just before the Japanese attack on Pearl Harbour, in 1941. Apparently, as a British Secret Agent, I wouldn't support the vile agenda of Churchill and Roosevelt, to allow the Japanese attack on Pearl Harbor, in order to get isolationist United States into WWII, as a British Ally. To me, allowing that attack seemed cowardly and evil and I don't think highly of Churchill or Roosevelt.
I believe I had just returned from informing a certain United States Naval Intelligence Officer, nicknamed "Flash", about what was going on, who had connections to British and American Intelligence, hoping there was something he could do from his side, to prevent the Japanese attack. Apparently, my fellow British agents knew what I was up to and were ready to ambush me by the time I returned to my office of work.
Though I may have been able to lash out and kill the agent who used a pistol at close range, to shoot me through the throat, before I dropped dead, the idea wouldn't have been very appealing, as I would have had friendly emotional ties, to my fellow agents. Nonetheless, it would have been very disappointing to me, that I couldn't help prevent the attack on Pearl Harbor. Then, on the other side of life, I would have been helping to secure and succour the individuals who died at Pearl Harbour, including the sailors in one of the U.S. ships, who spent hours or days dying in one of the sunken ships.
I have attained an awareness of the previous lifetimes of myself and others and karmic-reincarnational patterns associated with that, through intuition, synchronicity, things I've read, what I've been told, one brief dream or vision and a recognition of obvious karmic-reincarnational patterns. This is connected to the fact that I've known about reincarnation and past lifetimes for a long time, through many lifetimes. In this lifetime, I apparently did something unusual, to kick off my awareness of these things.
There's a certain book, The Iron Mistress, about an historical character who died at the battle of the Alamo on March 6, 1836. The book was published in 1952, the year I was born. I believe I caused my mother to have that book in her bookcase, before I was even born. Then, in 1970, when I was 18, I picked that particular book out of my mother's bookcase and read it. I had never read any of those books before. Yet, that particular book gave me the intuitive impression, that I was reading about my own past lifetime.
Over the years, that has extrapolated to an awareness of the karmic-reincarnational patterns of myself and others, through history and legend, including Biblical and even through science "fiction", which isn't always strictly fiction.