Two potato varieties on the same plant

Look at what I just got out of a weedy patch. Two potato varieties on the same plant. One is ruby lou and the other one I don't know.
Potatoes are a bit weedy here, once planted they will pop up in the same bed over and over again.
But doesn't this plant defeat the laws of genetics or am I missing here something?

Based upon my own experiences growing potatoes, the brown tuber is the "mother" of the plant, the pink one is the new tuber that the plant produced.

Some of the varieties I grow have the seed (or mother) tuber rot away, thus it is never seen at harvest time. Sometimes it fails to rot completely away and I find a slimy, gooey, half rotted mother tuber. In other varieties the mother tuber does not rot away, but it can be readily distinguished because it is darker, browner color than the fresh new tubers. Because I work with novice gardeners in the community garden, I tend to make a nick or slice in the seed (mother) tuber at the time of planting so that it can be easily recognized at time of harvest. Almost all new people working in the garden have difficulty telling the mother tuber apart when they first start working in the potato patch.

Ruby Lou is a new one on me. I haven't seen it in my region. Is it a boiling type? Wax? Baker?

I am in Australia so you would not get ruby lou but I like the variety. NOw I understand that yes usually I have a rotten potato as a mother. It is so easy to grow potatoes here that I don't give it too much attention. Apparently if you are in the mountains they don't get diseases.