dnd 5e – One PC Grappling multiple creatures

The section for grappling in the Player’s Handbook reads:

The target of your grapple must be no more than one size larger than you, and it must be within your reach. Using at least one free hand, you try to seize the target by making a grapple check, a Strength (Athletics) check contested by the target’s Strength (Athletics) or Dexterity (Acrobatics) check (the target chooses the ability to use). If you succeed, you subject the target to the grappled condition…

PHB 195

As long as you have a free hand, and the target meets the criteria, you are able to attempt a grapple.

The section goes on to say:

When you move, you can drag or carry the grappled creature with you, but your speed is halved, unless the creature is two or more sizes smaller than you.

A grappled creature can be moved with you, but it halves your movement speed. Moving the second creature halves your movement speed again to one quarter speed.