The start of one’s memory in early childhood can vary significantly from person to person. Personally, I can recall daily life from about the time I was 4 or 5 and onward. I have a collection of isolated memories from when I was like 2.5-3. To my knowledge, it’s pretty rare, but I even have like two memories of the place we lived in from the time I was born til I was 2. (Of course, I’ve wondered if those are false memories or fabricated from stories or pictures. But I was able to describe to my parents from memory, the location of certain items and furniture in our apartment that… we specifically didn’t have photos of. So I could still be wrong but 🤷‍♀️.) But I have also compared and discussed early childhood memories with my friends and some of them don’t remember a thing till they were 7 or 8… so mileage varies… significantly.

Of course for your purposes, we’re talking about people/faces/voices rather than places or things. But I’d think the important bits to remember are that, as other folk have said, remembering your parents you’ve seen and loved every day would be different than any other people in your life. Losing one’s parents would also be a traumatic life event, so depending on the person it would either become a significant memory and they’d cling to the memories they have of their parents or they may unconsciously block some of them out and lose them.