Answer
(Fatwa: 573/484/B=1433)
Each father loves his only child but it does not mean that you kiss his grave after his death. It is not lawful to kiss the grave. It is useless, to fall in the doubt that the dead one feels our presence or not by going near the grave. You should visit the graveyard for your reformation i.e. remembrance of death and the concern of hereafter. When you go there pay salam and recite verses of the holy Quran whatever you like and do isal-e-sawab and supplicate Allah the Almighty that your child becomes an asset for you in hereafter. In order to have children in future keep on reciting the following dua extensively:
رَبِّ لَا تَذَرْنِي فَرْداً وَأَنتَ خَيْرُ الْوَارِثِينَ
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband