How to mend my relationship with my only sisterinlaw?

We were 2 siblings me and my 5 yrs younger brother and our mom and dad ours was a happy family. Somehow once my brother got married things between me and my sisterinlaw never seemed to be working but i kept on working on this relationship but somewhere she started withdrawing and also started pulling my brother away from me but we were always in touch he would hide and talk to me and visit us as well. Unfortunately I lost my brother due to cardiac arrest and after that I also lost my father who was already on deathbed.I have already lost my mother 7 yrs back. I feel so lonely and depressed and my sisterinlaw does not talk to me and she even does not let me talk and get in touch with my brothers children . I have tried my level best what do i do please help. I am married and I have my husband and 2 sons getting on with life is becoming difficult for me