Who has more right
    to custody of the child – the father or the mother?
Question

                My question is as follows:I married a sister who had a
      child with her husband before me. The little brother is currently three years old.
      If their is any evidence to show clearly my wife's right to visitation. And the behavior
      of the Sahaabah and their implimention of the hadeeth,"And the women has more right
      unless she remarries." How did those men who took custody of the children give their
      former wife her right to the child. Please help us we are truly being oppressed
Praise be to Allah.The best way for a child to be brought up is with both
    of his parents, because if he is cared for by both this will strengthen him physically,
    enhance his intellectual development, keep his soul pure and prepare him for life.
If it so happens that the parents separate, then the mother has a
    greater right to custody than the father, unless there is reason not to give priority to
    the mother or there is a reason to give the child the choice in the matter.
The reason why the mother is given priority is that she is the primary
    caregiver and is the one who breastfeeds the child; she is also better able to care for
    the child and take care of him. She has more patience than a man in this regard, and has
    more time than he does, so the mother is given priority in the best interests of the
    child.
It was reported from Abd-Allaah ibn Umar that a woman said,
    O Messenger of Allaah, my womb was a container for this son of mine and my lap was a
    haven for him, and he drank from my breast, but his father is claiming that he should take
    him from me. The Prophet 
 (peace and blessings of Allaah be upon him) said:
    You have more right to him (to custody of him) so long as you do not remarry. (Narrated
    by Ahmad, 2/182; Abu Dawood, 2276; al-Haakim, 2/225. Classed as Saheeh by al-Haakim).
    Yahyaa ibn Saeed said: I heard al-Qaasim ibn
    Muhammad said:  Umar ibn al-Khattaab had a wife from among the Ansaar who bore
    him Aasim ibn Umar, then Umar divorced her. Umar came to
    Quba and found his son Aasim playing in the courtyard of the mosque. He took
    him by the arm and seated him in front of him on his riding-animal, but the childs
    grandmother caught up with him and fought with him over the child until they went to Abu
    Bakr al-Siddeeq. Umar said, (He is) my son! and the woman said,
    (He is) my son! Abu Bakr said: Leave them alone, and Umar
    did not answer back. (Narrated by Maalik in al-Muwatta, 2/767;
    al-Bayhaqi, 8/5). Ibn Abd al-Barr said: this hadeeth is well known
    with a variety of isnaads, complete and incomplete, and is accepted by the scholars.
    According to some reports, [Abu Bakr] said: the mother is more
    compassionate, more kind, more merciful, more loving and more generous, and she has more
    right to her child unless she remarries.
Abu Bakrs description of the mother as being more compassionate
    and more kind is the reason why the mother has more right to the custody of her young
    child. And Allaah knows best.