Nez

I think he will gradually remember as he has to confront the Eraser especially more intensely if he turns out to be his dad. Since he has memory scan ability, once they find more about the Eraser and the past he might actually regain his memories or even kind of scan his own memories. DB remembering almost nothing about his childhood is probably the very key to all this. I think if he starts to remember, the hell's gonna break out. Also there is another possibility that his memory is gone because of the trauma not the Eraser. In any case, I feel like him remembering his past will probably reveal many things and connections.

I feel like the reason why DB doesn't remember his childhood is because the Eraser has erased his memories. Which makes me think that the Eraser is DB's dad and DB has witnessed his killings including his mom's murder. Also, I think DB and SM could actually have some connection through their childhood and that might be the reason why DB says that her death would hurt him the most in the next episode's preview. In a sense DB could be a bomb waiting to be activated by the Eraser, if he hasn't already been. I guess we will know more once he starts to regain his memories and we find more about his passing outs.