Here's what I found. Distilling white wine into brandy, using a pot still, is do-able: and, its pretty easy. I fired up my Copper Alembic 7,5 liter electric. I poured in 4 x 187 ml bottles of Bella Sera Pinot Grigio (750ml.) Adjusting for the sub-standard thermometer supplied with the still, I took the first 50ml off for heads and set aside for paint thinner. I took the next 50ml off for hearts. These tasted and smelled just like brandy. I had a bottle handy to compare to. Of course, the oak and age was different; but, the basic ingredient was quite good enough to drink. I took 50ml more off for tails. These smelled foul and I kept them for the next run.
Total: 150ml of alcohol = 20% abv (the label stated 12.5 abv)
So, yes, one may certainly distill store bought wine into brandy.