Cecilia

Cecilia is the oldest kid of Catherine Flanders/Swanson.

Story
Her first appereance was in S01E05, where Ned introduced Catherine and her children to the Simpsons. She was next seen in S01E12, where Ned proposed to Catherine at a party. She also appeared at S02E01 in the street with Nelson. They kissed and are now dating. She appeared in Ned & Catherine's wedding in S02E04.

Description
She is impossible to fool, just like her mother. But unlike her mother, she can beat anybody up if she wants. She is smart like Lisa, but a bullie like Bart. She has got the beauty of her mother, Christianism of her step-father, tricking ability of her brother, and finally, her fantasizing ability of her sister. She is a truly great person, and that's probably the reason why Nelson loves her so much.

Relatives
Mother - Catherine Flanders/Swanson

Father - Mr. Swanson (deceased)

Step-father - Ned Flanders

Sister - Christina Flanders/Swanson

Brother - Cooper Flanders/Swanson

Step-brothers - Todd and Rod Flanders