How lovely! Are you sure they will stay small?

If I keep them in the same container they will stay smallish. I posted a few years back about 'Black Coffee'. I had 3 or so plants of it, one in a rinse cup that stayed very small for a few years (until it died) and a big one in a six inch pot and then the others were in like four inch pots. Obviously the plant filled their pots but we can contain them if we stay at it.

Those are beauties! I love rex begonias - they just don't love how I forget to water them in the winter when the house is extremely dry from the furnace running.