Need help in Maintainance Money issue

After 1-2 years of my sister mariage, there sasural family members were not behaving well with her. When she saw 5 months pregnent, and she had pain issue but still there family wants him to home work. When she denied they send her to my brother house and said she dont work in this house. She gave birth by help of my big b and bhabhi and even after baby came, there family member behaviour didn't change, so my sister left home and come back to mothers house along with child and stayed for around 2 years with parental leave in office bcoz of covid. When parental leave was over, she had to relocate back but she took flat on rent and initially asked his husband for financial help as she had to take care of new born baby with flat rent money. But since last 1 year, his husband stopped sending money and now they even don't call and seek his child. (reason is just that my sister don't live there so why did they give financial help to mother or child). Please help how to get financial help.