Life Insurance Cover is bought to cover risk of loss of breadwinner. If you wife and parents are earning and somebody is dependent financially on them, then buy life insurance minimum of 10 time of their income.
Use these calculator for your parents -
Human Life Value Quick Calculator - http://www.policywala.com/hlvcalculator.php
Life Insurance Income Replacement Needs Analysis Calculator - http://www.policywala.com/lincalculator.php

For your wife check here -
Home Spouse Life insurance Income Replacement Needs Analysis Calculator - http://www.policywala.com/hwncalculator.php