In the novel "The Mars Project" by Wernher von Braun humans fly in convoy to Mars. Is it being considered seriously at all today, to send several spacecrafts together?
Most proposed missions to Mars require pre-deployment of some payloads on Mars before humans arrive. If instead sent together with the crewed spacecraft, I can imagine some potential benefits. In an emergency the crew might evacuate to the surface habitat in flight. They could sacrifice one of the spacecrafts if they have better need for the fuel meant to land it. At Mars, they could teleoperate the landing of the spacecrafts, or maybe land in formation to make sure they all land within reach for the crew.
Drawbacks might be the risk of collision, difficulties of docking spacecrafts to transfer fuel, crew or cargo. And it doesn't seem possible to reliably make several simultaneous launches from the ground (although the military has that ability with solid launchers) so the convoy would have to get together in orbit.