Fenella is the sister of Basil, Baron Feldman of Frognal. But she doesn't have any title. Basil is a life peer as a reward for his political work.
Had to pay for her own ring in Carry on Screaming! (1966) which cost £9.
Despite persistent published reports, Fenella Fielding was NOT the sister of actor Marty Feldman. The two are not related in any way.