Friend
Also called Bǐ Jiān, the Companion
A chart describes tendencies in a traditional system. It cannot decide health, money, law, marriage or children.
In the classical sources
比肩者，兄弟也。
Shoulder-to-shoulder means brothers.
淵海子平
About this relation
比肩 means shoulder to shoulder, two people standing level. Find it by taking the day master and looking for another stem of the same element and polarity: for a 庚 day master, any other 庚 is a Friend, and 辛, the same metal in yin, belongs to Rob Wealth. Hidden stems inside branches get the same test. 淵海子平 gives the name no chapter of its own, and 神峰通考 treats it only together with Rob Wealth, so it is known from tables and from sections on siblings.
淵海子平 reads it straightforwardly as kin, with 甲 seeing 甲 as a brother, and its table for 乙 adds friends. 神峰通考 is blunter and says the same-polarity pairing harms wife and child, while a yang stem paired with a yin one spares the wife. That sentence comes from an old manual written from a husband's seat, and 淵海子平 draws its lines elsewhere when it reaches Rob Wealth.
What a Friend does depends on the company it keeps. A note in 神峰通考 says that where wealth is heavy and the self weak these siblings are welcome help, and that where wealth is light and the self strong they take away. Popular modern books use the name for peers, rivals and independence, an extension the old passages only hint at through the word for brothers.
Where this text comes from
The quotation and the attributed statements follow the Wikisource texts listed here. The relation rule is the method used by the calculator.
The English name follows common modern usage. The wording here is our own plain summary.