noun
growing old together (as a married couple)
Poetic or literary term for a married couple aging together in harmony. Often associated with auspicious imagery like paired pine trees.
See also: 相生い
相老いの松は夫婦円満の象徴とされる。
The paired old pines are considered a symbol of marital harmony.
二人は相老いを誓い合った。
The two vowed to grow old together.
Compound of 相 (ai, 'together') and 老い (oi, 'aging'). The alternate form 相生い uses 生い (oi, 'living') to emphasize shared life rather than aging.