Hi 'hooks'.
My favourite Bonsai material - figs! By the looks of your fig it appears to be a variegated ficus benjamina. If you want to combine the trunks it's a very easy process. Take all three trees out of the pot, put them together and remove any roots that are in the way on the insides of the trunk. Strip some bark from all three trunks on the inner sides and making sure the stripped bark edges are touching each other (cambium to cambium), bind it all together with grafting tape - not wire! Figs grow too fast to wire the trunks together because before you know it you have some nasty scars that are almost impossible to repair. Try and put the trunks in a position where the branches are growing out and away from the centre. Repot the tree(s) and leave without disturbing till you see the edges of the bark you stripped back beginning to callous over. A really good idea with any figs is about a week or two before you want to work on them, give them a big boost of fertilizer - well rotted Cow manure is about the best, chicken manure second. If you don't use either of these then any fertilizer is ok but if you use chemical fertilizers then stick to the recommended dose. Don't worry about burning the roots with strong animal manure - it won't happen with figs. I've been doing this for well over 20 years and never burned a root yet. The theory is that the tree takes up these nutrients, you work on it and the tree goes crazy putting out new shoots and leaves and roots. This method works for us here in Queensland Australia. I wouldn't recommend this method for other trees, some really are sensitive to strong manure and can't handle it and severe damage can - and most likely will occur. The fertilizer boost isn't necessary though, it's just the method we use. In my opinion you will get a better tree quicker by combining the three trees than by separating them.
Hope this has given you a bit of food for thought.
Taffy