Getting rid of underage squatters.

Without details I'm just guessing but eviction according to Florida law is what you need to do.

I don't know if these are friends, relatives, friends of relatives, something else.

Here is the statute - http://rhol.com/csu/evictions/Florida/FloridaSteps.htm

Underage? Call the cops before you end up with a slew of fines. Board place up if possible.

Total lack of background info leads my spidey senses to believe this is a family member or other relative, not a "break down the door and squat" person.

If they broke in, they are trespassers.
If you let them in, or even let one of them in and he brought his friends, you have to evict them through the court.
Florida has the shortest eviction process in the US.

There really is no such thing as a "squatter" and there are no "squatter laws"

You will need to explain who they are, what is your relationsihp and how they got to live on property and how long there

Exactly how old are they? How did they start staying there?

Exactly how old are they? How did they start staying there?

And are they actually living there? Where are their parents or guardian?