Gilbert de Blackburn of Ryssheton, 1st Lord of Rishton and 1st of the Rishton line - Gilbert father

This is on the Geni for Sir Adam de Blackburn , Knight
1175–1206

Birth 1175 • BLACKBURN Lancashire England
M. Alice de Blackburne, b. Abt 1179, Cuerdon, Lancashire, England. Married Abt 1195 , Blackburn, Lancashire.
Children:
1. Henry de Blackburne b. 1196, Rishton, Lancashire.
2. Agnes de Blackburne b. 1202.
3.John de Blackburne b. Abt 1205, Blackburn.

So it seems clear that the first Rishton was Henry, son of Adam. Gilbert was his son.