PUZZLEBOXX

Let's start with Adam.

He has the same number of brothers as sisters, so let's add one of each.

Now count - to see how many brothers and sisters each girl has.

The girl hasn't any sisters so that's not the solution.  So ...

Now count - to see how many brothers and sisters each girl has.

(Remember not to count the girl as one of her own sisters.)

If it's twice as many brothers as sisters - that's a solution.  If not...

Now count - to see how many brothers and sisters each girl has.

If it's twice as many brothers as sisters - that's a solution.  If not...

Now count - to see how many brothers and sisters each girl has.

If it's twice as many brothers as sisters - that's a solution.  If not...

Are you sure you're counting properly?

You should find that there are 4 boys (Adam and three brothers)

and 3 girls in the family altogether.