1) The man had two sons, both of whom disobeyed him at one point or the other. Everyone is a child of God. Everyone sins. God gives everyone a chance to obey.
2) The first son repented later. It's never too late to repent. God welcomes the penitent.
3) The second son said he would obey, but didn't. God is more displeased with hypocrites, people who have said they will obey God, but then don't, than He is with those who have never made a commitment in the first place.
Are you either of these sons? Have you refused to come to God until now, but find yourself now willing to obey Him and be welcomed by Him? Or are you the second son? Have you made a commitment to God, have you called yourself a Christian, but now need to live that commitment out more fully?
Everyone is God's child and He welcomes into His favor all who repent and choose to obey His perfect and loving will.