Your sons are very happy with you. Their mother is living with her paramour. More importantly, their mother has no love and affection for her child. These facts are in your favour therefore, you can retain custody.
Welfare of child
The welfare of child is the paramount consideration for custody. The court has to decide custody on the touchstone of well being and welfare of the child. Custody is a human problem; it cannot be decided on the strict rule of legal provision.
In Nil Ratan Kundu and other vs Abhijit Kundu AIR 2009 SC (Suppl) 732, the Supreme Court has held that a court while dealing with custody cases, is neither bound by statutes nor by precedents. It should be solved by human touch.
In your case, children are happy with their father and grandmother. The father and mother are both natural guardians under Section 6(a) of Hindu Minority and Guardianship Act.
Also read: Visitation right
In Githa Hariharan vs. RBI and another AIR 1999 SC 1149, the Supreme Court has held that the mother’s right under Section 6(a) stands at par with the father if the father is absent. Father and mother both are natural guardians but welfare of the child is the central point in determination of custody rights.
The Court will examine the circumstances of your case. It shall also consider the carelessness and character of the mother while deciding the custody. Their mother has breached matrimonial loyalty and is living with her paramour. The ambience of such a family would be harmful for the children. Therefore, your wife cannot take custody of children.
Taking custody of children from the father
Being a mother, she is claiming custody. But she lacks the ground for taking custody of children from the father. The court cannot ignore the fact i.e. “welfare of the child” while deciding custody. The ultimate goal of the court, in custody matters, is to secure the future of minor children.
In Tejaswini Gaud vs. Shekhar Jagdish Prasad Tiwari and others AIR 2019 SC 2318; the Supreme Court reiterated that:
The welfare of the child has to be determined owing to the facts and circumstances of each case and the court cannot take a pedantic approach.
You are taking care of your children very well. Their education and moral training would be fairly well in your custody. They are psychologically and physically living in the secure atmosphere of a family. Living with mother’s paramour would be insecure for them. So I think you will retain their custody. Mother cannot take their custody from you.