suffix
Suffix attached to a person's name in an address to indicate that the mail is to be delivered to that person at the household of the named head of household. Used in formal written addresses.
封筒に「田中一郎様方 山田太郎様」と書いてください。
Please write 'Yamada Taro-sama, c/o Tanaka Ichiro-sama' on the envelope.
請求書は、佐藤様方に送付いたします。
We will send the invoice care of Mr. Sato.
気付 is used when sending mail to a person at an organization or company, while 様方 is used when sending to a person at a private residence.
Compound of 様 (sama, honorific suffix) and 方 (kata, direction/person). The reading さまかた is standard; さまがた is a less common variant.