2 breakers wired to a single circuit
I'm doing some renovation work and have encountered a strange situation (to me) while mapping out the main breaker panel.
On more than a few outlets and lights, two circuit breakers must be on for the outlet or light to be "on". This is not for all circuits, but for well more than 1/2 of the house at 120V, including my swimming pool pump (240V). There are two circuit breakers marked "main lights" in particular in which one of them has to be on in conjunction with another one on the panel which seem to be the main culprits.
My question is, how concerned should I be with this wiring? Is it normal/acceptable? The house was constructed in 1927 and is a mixture of K&T and Romex. The dual breaker situation seems to exist in both types of wiring.