If they really are coming out of the same seed, then they will probably share the same tap root, and even if they didn’t, by the time you transplant them, they will have their roots too tangled to be able to be separated.
They might be like conjoined twins, almost sharing the same legs but having two separate torsos, if they really came out of the same seed.
However, if they did come from separate seeds, and they are still very fresh above ground seedlings, the two separate tap roots are not likely to be tangled yet, and they likely have no roots off shoots yet either. If you think they might be from separate seeds and need to be separated, the earlier the better.
Did you germinate them in a soil like media or some other rooting media like rock wool or something else?