I have found that adding albums to my Memories has helped me keep my Memories organized. However, I don't see any way to organize my parents memories using albums .
I believe there have been several suggestions that we be able to have "sub" albums, just like sub folders. That would help a lot. For the time being, please note that you can put a memory in multiple albums. That may help you.
So, my father's line, Swihart, is currently one of my albums. I have a lot of stuff.
BUT, my paternal grandmother was the daughter of Danish immigrants and I have so many artifacts from that line that I created a separate album for all my Danish photos, letters, etc. Only items about my paternal grandmother are in both the Swihart and Danish albums. All memories having to do with her parents, grandparents, relatives further back and the many current day cousins are in only the Danish Album. All memories having to do with my paternal grandfather, my father, aunt and uncle are in the Swihart album only.
I did that because most of my Swihart relatives are not descendants of the Danes. Most of my (MANY) Danish relatives barely notice my maiden name is German. Personally, I would prefer that my Danish album could be a sub-album of my Swihart album, but not right now.