ㄕㄨㄤ宿ㄙㄨˋㄕㄨㄤㄈㄟshuāngsù‑shuāngfēi

双宿双飞
  1. 鳥類雌雄行止相隨用來比喻夫妻起居相依形影不離 雙宿雙飛白頭偕老」。

lit. to rest and fly together (idiom)​, fig. to live in each other's pockets, to be inseparable