Unless they have put more than one seedling in a pot, which isn't likely, you are dealing with one tree that has been cut back to create multiple trunks, as Alabamatreehugger has said. Even if there were 5-7 trees together, by this time, the roots would be well intertwined, and would NOT be happy to be disentangled from each other. Dividing can work for perennials, or if you had planted a bunch of tree seeds in a pot and then dealt with the babies at a few inches tall, but most semi-mature trees won't do it. Suckering shrubs maybe, but that's not what you are dealing with here. I can appreciate your wanting the shape that you want and the number of trees that you want, but I don't think this is how you will get it. Keep looking..... HOWEVER if they aren't too much money, so you wouldn't mind too much if it/they died, it MIGHT be worth buying one and trying. I think I would wait until fall or early winter to "operate", when the tree won't be actively growing and will be as dormant as they get, so you may need to pot this one on to a larger pot over the summer. Carefully removing the soil from the root ball (try using a water spray), at least at the top, would let you see what the trunk/root system really looked like, and then you could make up your mind if this is at all feasible. Since you do have experience dividing plants, I think it would be up to you to decide. They MIGHT all die, and they MIGHT live, I wouldn't want to say for sure. If it were me, and I really wanted this, and couldn't find what I did want, AND it weren't too much money, I think I would have a go - experimentation is how you learn more after all.

what kind of patio ... ken

The only source that I know of is the New England Wild Flower Society (www.newfs.org).

could be a young magnolia but It does look like a fig if you select 3-4 of the strongest branches and prune them at about 1ft from the soil, it will grow in a nice open habit...or select one and prune it at about 2ft, stake it and it will be more of a half standard style the whip should be pruned at about 1' as well, this will induce branching below the cut