Cassandra, David and Lachlan are brothers and sister.
They range in age between $1$ year and $14$ years.
Can you figure out their exact ages from the clues?

Lachlan's age and David's age added together is $10$ years.
Cassandra's age and Lachlan's age added together is $15$ years.
David's age and Cassandra's age added together is $19$ years.

This problem was made up and sent in by Cassandra from Cambridge in the UK. Thank you Cassandra!