Siobhan Fairbrother

Siobhan Fairbrother is one of the twin daughters of Barry Fairbrother. As she is in the same school year as the other teenagers in the novel, she is presumably about the same age.

Etymology
Siobhan (approximate English phonetic spelling "She-vaun") is a Gaelic name meaning "God is gracious". It is a cognate of the English name "Joan" or "Joanne", and of the Scottish name "Judith".