Maintenance to adopted daughter

One of my aunty (pinni) adopted one child who is her brother's daughter.  Her brother is working in Singareni Colleries and he has two daughters (except one daughter), who got already married.

Now, aunty's husband got expired and she requested her brother to support some amount, but he was refused and not interested to call.

My aunty wants some amount from her brother for her daughter's maintenance.  Can we file any case
against her brother for getting maintenance charges.

Please suggest