Going into the main breaker panel, can you put 2 romex wires through one romex connector (3/8")

Also if allowed, can you run (1) 6/3 and (1) 8/3 romex wire through a 1" romex connector?

Thanks all.

Most connectors are only rated for one cable per. Need to check the specs on each connector to see what it can handle. Certainly not with the two large cables in the 1 " connector.