Four families were on a joint outing. In the first family, there were three siblings, namely Alice, Bětka, and Cyril. In the second family, there were four siblings, namely David, Erika, Filip, and Gábina. In the third family, there were two siblings, namely Hugo and Iveta. In the fourth family, there were three siblings, namely Jan, Karel, and Libor. On the way, the children split into groups such that in each group, all the children had the same number of brothers and no one else.

How could the children have split up? Determine all possibilities.

(V. Hucíková)

Hint. Count the brothers of each child.
In each group, there are only children with the same number of brothers, and the number of brothers each child has is known from the given information. Therefore, the children could be divided in only one possible way. It is sufficient to sequentially determine the number of brothers each child has and form the corresponding groups.

- Alice and Bětka have one brother, Cyril has none.
- Erika and Gábina have two brothers, David and Filip have one.
- Iveta has one brother, Hugo has none.
- Jan, Karel, and Libor have two brothers.

Thus, the children were divided into three groups:

- Erika, Gábina, Jan, Karel, Libor.
- Alice, Bětka, David, Filip, Iveta.
- Cyril, Hugo.