My grandmother has two sons of wich one is my dad and the younger one is my uncle ,so it was like my uncle had

my uncle was children less so he adopted my youngest new born sister,all was fine ,untill now 10 years later,by artificial implant my aunty is having a child n have some what started ignoring my sister,and my grandmother too is all of a sudden very strict ,harsh and abusing towards her,and my mom coudnt see all tis torturing to her daughter and when casually just like children asks tat i tink ia adopted my mum told her the truth ,nw every body is after her ,nagging and taunting her is she right and wat should we do now,to calm all tis