Who was jijabai ? 

why we called him second wife of ramji?

Why we are knowing him?

First answer that I say is 

She (jijabai ) was the second wife of ramji sakpal and she was the stepmom of bheem.

When ramji sakpal's first wife mrs. Bhimabai Sakpal dead because of headache problem on 20 december 1896.

After 5or 6 months jijabai a dalit widow came in satara because from her in law's house she was thrown. 

And in satara she and her family got to know about ramji whose wife had dead and according to ramji he did not want to remarry but ramji's sister forced him to marry and he married with jijabai. On first night of marry, Ramji proposed a proposal that she couldn't be a mother because ramji already had sons and daughters but main motive of ramji was that bheem was his smallest child and he just wanted to teach bheem and nothing else.  Bheem was also not in favour of ramji 's second marry and if i talk about jijabai's behaviour she was very  upset from Ramji's proposal and this started him getting angry with  bheem and his family.  And her behaviour was not so well. 

She didn't be the right choice for ramji and her mind was also shaped by uppercast peoples because they were angry with bheem and because of jijabai's behaviour ramji's whole family got destroyed.  

She tried to set all the book's of bheemrao on fire. But she didn't successfully every time.

When they move from satara to mumbai she didn't change her attitute and be angry person.  If we talk why she became like that then we come across many reasons, first reason could be because of his community in satara and second reason was she herself and i think third reason was ramji also.

His community in satara filled herself that bheem and you and your community is of lower cast and bheem should not take education and because of bheem whole family had to face problems and scarcity of food because people in stara(upper cast people) refused to gave jobs to ramji and his family, They thought that if they gave job to ramji then bheem would take education and might be that he would became barrister so, they faced many problems and not all upper cast peoples are bad . Some if them gave job to ramji. Might be that they were reasons why jijabai disliked bheem.

Second reason was ramji also because ramji said on his first night of marriage that he would not have any child from jijabai because ramji already had bheem and other child. From this situation jijabai was also started jealousy from bheem. 

Third reason was she herself,  If she wanted to be a good mother and a good wife then she could but she didn't be a good mother and good wife also.