relationship with my late husband family member

my husband died few month before after suffering from terminal stage cancer .He was a good muslim and husband .He did so many things for his parents and sisters and brothers to make their life nice and smooth . .But he did not get time to do something for his 7 years twins and wife .My in- law family not nice to me , they hurt me ,feel me down and inferior and also they do backbiting and false accusation . when my husband died , he had some loan and that tough time they did not help me with anythng but they did hurt me a lot , But we did so many thing for them but but they act like they deserve that and I am only their maid ,they talk like disrespectful manner .I can't handle that .I don't have anything here except my boys and usa citizenship .I have to work to raise my boys .I love my husband and I decided I will stay as a single mom for them .I know it is tough but i I love him more than anything this world .My question is __Is it sin if I avoid my in -low family member ?,somebody told me breaking relationship is against the muslim law . ? But when i hear bad thing ,back bitting ,false accusation I can't go foreward .It hold me backward ,I don't have any thing here . I have to go foreward .Please answer me --can I avoid them .?