What type of behaviour do you want from your sons, good or bad?
You want your sons to talk to you with respect, to tell you their secrets, to have a sweet conversation with love, to feed you lovingly while blowing the fan, to talk to you about your happiness or sorrows twice a day, to serve you with their own hands instead of the servants when you are unwell, to take you to a pilgrimage and to a temple for having darshan (glimpse of God), donate according to your wish, then do one thing, from today itself do all of these things to your parents without any selfishness and condition. Then have faith that your sons will give you the same respect as they have seen their parents do or heard from the neighbours.