Do familiars and animal companions earn XP?

Question

Rules as Written, experience is split evenly in adventures between all creatures that meaningfully participate.

Dungeon Master's Guide (1st printing, pg. 260):

When adventurers defeat one or more monsters-typically by killing, routing, or capturing them-they divide the total XP value of the monsters evenly amongst themselves. If the party received substantial assistance from one or more NPCs, count those NPCS as party members when dividing up the XP.

So if there's a warlock with a familiar, that's an NPC, to my mind. Do Familiars gain levels? What about beast companions, or unofficial beast companions gained via magic or animal handling?

UA Ranger Beast Master companions seems to level up, since it gains proficiency, ASIs, and hit dice... But that's tied to the Ranger's level

Answer 1

No. They are part of a class feature of the character, and considered as "part" of that character. They are not NPC, they are creatures under the control of the PC with strict guidelines.

The stats of those creatures are therefore bound to the controlling player's stats, proficiency and level in general, as they are part of that player's class features, just like a spell save DC.

They also don't act on their own. The ranger's beast companion must be instructed to attack every single round, for example.

The difference between those creatures and a real NPC is that an NPC has its own will and motivations. An NPC cannot be dismissed when convenient like a familiar can (and the familiar will never complain or rebel against the warlock). An NPC is under the control of the DM at all times, but the familiar and beast companion are under the control of the player. The DM should refrain from describing actions for those, as it would violate player agency.

Answer 2

No, because they don't count as NPCs

In short, familiars and animal companions do not take a share of XP because, being under a player's control rather than the DM, they do not count as NPCs. (The fact that they're acquired by a class ability is irrelevant to whether or not they gain XP; there is no rule to this effect in D&D 5th edition.)

As the question says, the rules on who gains XP are in clearly defined in the Dungeon Master's Guide, p.260:

When adventurers defeat one or more monsters—typically by killing, routing or capturing them—they divide the total XP value of the monsters evenly among themselves. If the party received substantial assistance from one or more NPCs, count those NPCs as party members when dividing up the XP.

Only adventurers and NPCs gain XP. Here's why familiars and animal companions count as neither of those:

1. They're not NPCs because the DM doesn't control them

NPC is clearly defined in the Player's Handbook, p.89:

A nonplayer character is any character controlled by the Dungeon Master. NPCs can be enemies or allies, regular folk or named monsters.

The ranger's animal companion is controlled by the player, not the DM:

The beast obeys your commands as best it can. It takes its turn on your initiative, though it doesn't take an action unless you command it to.

A familiar is also under the player's control (PHB 240):

Your familiar acts independently of you, but it always obeys your commands.

2. They're not adventurers because they don't have class levels

"Adventurer" is clearly defined as someone with class levels (PHB 11):

Every adventurer is a member of a class.

"Party" is clearly defined as a group of adventurers:

Each character plays a role within a party, a group of adventurers working together for a common purpose.

Animal compansions and familiars do not have class levels. They therefore don't count as adventurers or party members. Since they're not NPCs either, they do not take a share of XP or gain XP.