He's Phineas. This is ___ brother, Ferb.
He's Phineas. This is his brother, Ferb.
He's Phineas. This is ___ sister, Candace.
He's Phineas. This is his sister, Candace.
She's Mabel. This is ___ brother, Dipper.
She's Mabel. This is her brother, Dipper.