Theo Heap is the youngest grandfather of the Heap family and is Silas' uncle. Theo is one of the first generation of Heap brothers. He is a Storm Petrel that flies about the Marram Marshes on stormy nights.
On stormy nights in the Marram Marshes, Zelda keeps a lookout for any Storm Petrels which might be blown away to the marshes and hopes to meet her brother again one day. There was an instance when a Storm Petrel came to sit on Zelda's roof one stormy night and it beccame clear that it was Theo Heap, since he sat on the roof of Zelda's Cottage and said to himself that she had always had a talent for seeing the truth in the Pond.
He is a ShapeShifter. When he became old he decide to permanently shift into a Storm Petrel.
Theo is brother to Benjamin Heap, and Zelda Zanuba Heap. His brother married Jenna Crackle and had six son's. His nephews are; Alfred Heap, Hengist Heap, Ernold Heap, Edmond Heap, Silas Heap and Garth Heap and one niece Lois Heap.
He is the Great Uncle of Silas' seven children;
Sam Heap, Nicko Heap, Simon Heap, Jo-Jo Heap, Erik Heap, Edd Heap, and Septimus Heap, and is the adoptive grandfather of Jenna Heap. He has a brother in-law named Titus Willow and a sister in-law named Thomasine Tremaine.