A proverb meaning that children do not understand (or appreciate) how much their parents care for them; children can be oblivious to parental concern.
子どもは親の心子知らずで、親の苦労が分からないことが多い。
Children often don't understand their parents' feelings; they are unaware of their parents' hardships.
親は夜遅くまで働いていたが、子供は親の心子知らずで遊んでいた。
The parent worked late into the night, but the child, oblivious to that, was playing — children don't know their parents' hearts.
家を出た息子を見送って、母は親の心子知らずを思い出した。
Seeing her son leave home, the mother was reminded that children often don't understand their parents.