Question Summary:
My mother sister’s little daughter is my razai sister (feeded milk of my mother in childhood) Can I marry with my mother sister’s elder daughter?

Question Detail:

My mother sister’s little daughter is my razai sister (feeded milk of my mother in childhood) Can I marry with my mother sister’s elder daughter?

Answer :

In the name of Allah, Most Gracious, Most Merciful

Assalaamu `alaykum waRahmatullahi Wabarakatuh
Considering the fact that the elder sister did not drink milk from your mother, it will be permissible for you to marry her. 
 
وكذا يجوز للرجل أن يتزوج أخت أخته من الرضاع
(بدائع الصناشع، 3/400، ديوبند)
And Allah knows best
Wassalamu Alaikum
Ml. Sajid bin Shabbir,
Student Darul Iftaa
Checked and Concurred by:
Ml. Yusuf bin Yaqub
Darul Iftaa, Madrassah In'aamiyyah