Diablo 3, loot system, PS4

VanBuzzKill nailed it on the head, but let's go a little in depth for an answer:

Loot drops on a per-player basis. Let's say, for instance, that you and your friend are fighting the Butcher. Once you kill him, great and bountiful loot and blood spill around the arena. The loot drops that you see will not be what your friend sees. For you, perhaps a Manald Heal ring drops; for your friend, perhaps a Unity set ring drops.

There is very little you can do to influence this, as there are no items or mechanics that can game the system like this.

The only way the game favors a lower level player in co-op is by upping their skills/damage numbers a bit until they reach a certain level. This has nothing to do with item drop rates.