It appears that you might be referring to the concept of “Tri Jyeshta”

“Tri” signifies the number three in Sanskrit, while “Jyeshta” represents one of the Nakshatras.

Let’s consider a scenario where a boy is the elder sibling in a household, and similarly, a girl is also the elder sibling. Both fall under the category of “Jyeshta Santhana.” According to tradition, they should avoid getting married on the “Jyeshta” star.

In another scenario, if both individuals have the “Jyeshta” star as their Nakshatra, they are advised against marrying on the “Jyeshta” star.

Whichever perspective is taken, the concept of “Tri-Jyeshta” should be avoided.

It’s important to note that while this is one rule, it is also prudent to take into consideration marriage compatibility, as this plays a significant role in marital unions.

Don’t judge based on a single parameter. If you’re examining Kundali matching, kindly watch the series of videos about Kundali matching. Take into account individual marriage yogas, time periods (such as dasha systems and progressions), and so on.

https://www.youtube.com/watch?v=I6naCaCwbHc&list=PLvmzzcGHiU3SfDXLV3hAxZpI1nNSbUF9M

https://www.youtube.com/watch?v=G69OFg99sb4&list=PLvmzzcGHiU3Qh5hWCaswpcYiaywzK5X-M&index=19