Question Summary:
Can I give zakāt to orphaned girls who live with their mother?

Question Detail:

My question is about Sadqah, my widow sister-in-law is living with us and we help her financially, emotionaly, physically and eithically. With the grace of Allah she manages her groceries and education for her three girls without any job or business but just from her late husnamd's savings and we do not take any kind of utility bills from her. I observe her giving zakat to servants sometimes so it means she is sahib-e-nisab but their living is just hand to mouth.
I want to help her by heart with the sake of sawab so I wanted to know below questions
1. Can I give Sadqah in form of money or any house hold electronics etc to help her?2. Can I give zakat to three girls, all are studying?3. Can I give kheirat?
Kindly guide me about the mode of help I should so to them, it will be my personal money not taken from my husband.
May Allah give you unlimitted Sawab for helping people like us.

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful. 
 
Assalāmu ‘alaykum wa rahmatullāhi wa barakātuh
 
May Allāh reward you abundantly for the kindness and generosity you have shown to your sister-in-law. 
The answers to your questions are as follows:  

And Allah Ta‘ālā Knows Best
Mufti Zameelur Rahman
Assistant Mufti, Darul Iftaa
[1]
فى الدر: ولا [يصرف الزكاة] إلى غني يملك قدر نصاب فارغ عن حاجته الأصلية...ولا إلى طفله، بخلاف ولده الكبير وأبيه وامرأته الفقراء، وطفل الغنية، فيجوز لانتفاء المانع. قال الشامي: طفل الغنية: أي ولم يكن له أب. بحر عن القنية. (رد المحتار، دار عالم الكتب، ج٣ ص٢٩٥ – ٢٩٨)
الدفع لولد الغنية جائز إذ لا يعد غنيا بغناء أمه، ولو لم يكن له أب، وقد صرح به فى القنية، وأطلق الطفل فشمل الذكر والأنثى (البحر الرائق، دار الكتب العلمية، ج٢ ص٤٢٩)