In most cases small ficuses are sold in a group of 3 for a bushier look I guess.
You can plant them in the same pot if you don't mind their roots get entangled. They will grow into a multi-trunk arrangement like your other trees. Growing them separately makes them stronger I think. Here is one of my ficuses that I separated from his 'brothers'. As you can see he got very strong and went under some pruning. First pic taken in March, the last a few weeks ago.
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thanks for the answer. may I ask what is that stuff at the top of the soil and what is it used for. Sorry to ask but I am starting this hobby so I know nothing

That is expanded clay. I grow my plants in these, without soil. This method is called semi-hydroponics. Ficuses (and all my plants) seem to like it.

Look up "hydroton",maltau.

One of these days I might just look into that method of growing. Seems easier to manage somehow...less watering comes to mind. lol

Definitely worth a try, I am so glad I did it!

Do you have to water these or not?

If you mean your cuttings in the soil by 'these', no, don't water for a while, there is enough moisture.
If you mean the plants in hydroton, then, of course you have to water.