Can a monk combine Martial Arts with Dual Wielding?

Question

I want to get a clearer ruling of unarmed strike. The way I've read/imagined it is using any part of a humanoid creature's body to hit something else. Fists, kicks, elbows, knees, headbutts, whatever. With a description like that, I imagine it's believable to be able to punch someone twice, go in for a knee-headbutt combo, or stab someone, then punch them. However, when looking at the "Unarmed Strike" in simple weapons, there are zero keywords. No "light" weapon for dual-wielding.

One of my players asked me about making a monk that "dual-wielded" unarmed attacks. Combine with Martial Arts, this type of fighting could yield one quarterstaff attack, one off-hand unarmed strike, and then a bonus unarmed strike from Martial Arts. I doubt I'd be opening any real kind of Pandora's box, but the question remains:

...Can a monk (or someone with Two-Weapon Fighting) "tri-wield" unarmed attacks without Extra Attack?

[Would it be overly gamebreaking to consider Unarmed Strikes light weapons?]

Answer 1

No. You can't dual wield Unarmed Strikes because they are not considered a Light weapon. That said, I don't believe it would be gamebreaking to houserule it that way.

However, in any case, you can't use two-weapon fighting and the Monk's martial arts on the same turn, because each uses a bonus action, and you only get one bonus action per turn. So your example of "tri-wielding" with a quarterstaff attack, an off-hand Unarmed Strike, and then a Martial Arts bonus Unarmed Strike would not be possible, because it would require two bonus actions to pull off.

Two weapon fighting:

When you take the Attack action and attack with a light melee weapon that you're holding in one hand, you can use a bonus action to attack with a different light melee weapon that you're holding in your other hand.

Martial Arts:

When you use the Attack action with an unarmed strike or a monk weapon on your turn, you can make one unarmed strike as a bonus action.

Note that the Monk Martial Arts ability does allow the Monk to effectively dual wield Unarmed Strikes, since they can unarmed strike as their main Attack action, and as their bonus action. And unlike regular Two Weapon Fighting, they get the bonus to their damage roll on the bonus attack as well.

Answer 2

As far as I can read a Monk could dual wield short-swords in order to use the feats "Defensive Duelist" and "Dual Wielder" which would give you a reaction to boost AC by proficiency bonus, and a flat +1 to AC while holding 2 finesse weapons. You could still use the Monk "Martial Arts" ability instead of "two-weapon fighting" just as you normally would to get the bonus to their damage roll on the bonus attack, since short-sword would count as a "monk weapon"