Those who follow the Way of Older Sibling might be members of a large family, part of a large group of young adventurers, but always on the older side of the group/generation, but not by much. They're the ones that the group looks to for the hard answers, but also avoids when things are winding down, or tension within the group needs to be removed, or they're bored.

Regardless of the light-hearted torment they give their party/family. They are the fiercest defenders of anyone within their sphere of teasing.  No one, ABSOLUTELY no one is allowed to treat their party with anything but the highest deference and respect, else they will face the true wrath of the Older Sibling.

The walkers are far less the stereotype of calm, cool and collected.  They tend to be jovial, boisterous, loud mouthed and sharp whitted. They are quick to anger and defend their party from outside antagonization. They also tend to lean more in the Chaotic levels of alignments, due to their unpredictable outbursts.

The Sharpest Wit requires The Sharpest Tongue

At 3rd Level, you gain Proficiency with the Persuasion and Deception.  You can now spend Ki Points to cast Vicious Mockery

No one does that to them but me!

At 6th level your joy of physically annoying your family/adventuring party can now be successfully weaponized.  You can expend Ki Points to perform acts of annoyance to painful effect to your opponents.

Each form of "physical affection" has it's own side effects, but the same damage as your current unarmed strike:

Noogie - Grapple the target and vigorously rub their skull until friction burns occur.
Purple Nurple - Grab and Twist the target's pectoral muscles and attempt to restrain them.
Wedgie - Pull their leg garb painfully over their face, blinding them.

You also gain Advantage on all Intimidation checks, as you have become more defensive of others tormenting your target(s).

I said leave them alone

At 13th Level,  up to three (3) times per Short Rest, an Older Sibling can spend a Ki Point and react to an attack on one of their party within melee range (10ft/1.5m) being attacked.

The Older Sibling can:

• Shield the target.
• Interception - reduce the damage the target takes by 1d10 + your proficiency bonus (to a minimum of 0 damage). The Older Sibling and the target must swap spaces.
• Counterspell the incoming spell by open hand slapping the caster (melee) or conjuring a spit ball to hit the caster in the face (ranged).

Let's Ro-Shambeaux for it

A 17th level Older Sibling monk unlocks the most powerful action in their arsenal. Known by many names, most are unable to be mentioned in any form of company, the "Ro-Shambeaux" is the ultimate weapon, and used sparingly. This weapon has been shown effective to practically all sentients, regardless of heritage, shape, or genitalia.  There is documented proof that it works on Undead, Abberations, Insects.  Even Jellies, Molds and Slimes, aren't immune, albeiet to lesser effect.

Known to be "use of Last Resort"  Older Sibling monks only wield this power when they feel it absolutley necessary.

Srike your opponent in their nethers using an unarmed strike, a hit will grant 5d10+5 Force damage.
The target then must roll a Constitution saving throw at disadvantage or increase their level of Exhaustion
The target must also roll a Dexterity saving throw at disadvantage or become Prone