noun
all one's family; the whole family
Used to refer to one's own entire family, often in formal greetings or announcements.
家内一同、皆様のご健康をお祈り申し上げます。
My whole family wishes you all good health.
新年のご挨拶を家内一同より申し上げます。
New Year's greetings from all of my family.
Similar meaning but uses 家族 (family) instead of 家内 (one's household). 家内一同 is more traditional and humble, often used in formal letters.
Compound of 家内 (かない, 'one's family/household') and 一同 (いちどう, 'all members').