It is parents’ responsibility to teach their children main spiritual truth. Of course, a grown-up child chooses the way by own will, and all we can do then is pray. But what we teach them (by word and, what’s very important - by our own example) stays in their heart and shows itself this way or another sooner or later.
“...the seeds of all sins are to be found in the children too; show them all the danger of sin on the path of life; do not hide sins from them lest through ignorance and want of comprehension they should be confirmed in sinful habits and attachments, which grow stronger and stronger and bring forth corresponding fruits when the children grow up.”
St. John of Kronstadt