Child custody after mother and father- maternal grandparents?

I am a mother of a 10 month old boy My in-laws are not friendly n supporting people. Recently my mom-in-law got my devar devraani divorced. Now her eyes are set on me n my husband. Earlier she had tried to separate both sons n their wives. I, was saved owing to my new born but my devraani fell pray to it. Now she dosnt genuinely love her sons, leave alone grandson. She wasnt happy only when I broke the news of my pregnancy to her. So now I want to ensure my childs safety.As far as I know after mother, father has the sole custody right for his son. Despite the fact that my husband loves our son a lot,he wudnt b able to take care of the child all alone. And I can't risk leaving my child in the custody of his paternal grans. I need legal help to ensure my child is safe, even If anything happens to me even by chance. So his custoday should be with his maternal grans that is my parents. How do I proceed in this regard Please help . Thank you