उन्होंने ही

they themselves

→ वह
phrase Uncommon #3,960
they themselves ही adds emphasis, highlighting that they were the ones who did it. उन्होंने can also refer respectfully to one person.
HI: उन्होंने ही खाना बनाया।
EN: They made the food themselves.

लेकिन घर तो उन्होंने ही बनाया है ना।

But they were the ones who built the house, right?

— Axone (2019)

उन्होंने ही फ़ोन किया था शांतनु को।

It was they who called Shantanu.

— Tribhanga (2021)

क्योंकि सब उन्होंने ही तो लिखा है।

Because they wrote all of it themselves.

— Tribhanga (2021)

ये सब उन्होंने ही प्लान लिया था।

They were the ones who planned all of this.

— AK vs AK (2020)