Jenison was baptized at
Heighington, County Durham, on 23 December 1696. From a family of Newcastle merchants, he was the eldest surviving son of Ralph Jenison of Elswick and Walworth, and his wife Elizabeth Heron (daughter of
Sir Cuthbert Heron, 1st Baronet of
Chipchase, Northumberland). He succeeded his father in 1704, and his grandfather Robert Jenison, in 1714. Jenison was
High Sheriff of Northumberland in 1716 and became a freeman of Newcastle upon Tyne in 1718. ==Career==