Answer
Wa `alaykum As-Salamu waRahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
You are allowed to marry the daughter of your grandfather’s cousin as she is not one of the forbidden categories of women we are not permitted to marry.
In his response to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
You are allowed to marry the daughter of your grandfather’s cousin as she is not one of the forbidden categories of women we are not permitted to marry. Here is the verse listing the women we are forbidden to marry:
“Forbidden to you are your mothers, and your daughters, and your sisters, and your aunts paternal and maternal, and a brother’s daughters, and a sister’s daughters; and your milk-mothers, and your milk-sisters; and the mothers of your wives; and your step-daughters – who are your foster children – born of your wives with whom you have consummated your marriage; but if you have not consummated your marriage, you will incur no sin [by marrying their daughters]; and [forbidden to you are] the spouses of the sons who have sprung from your loins; and [you are forbidden] to have two sisters [as your wives] at one and the same time – but what is past is past:[25] for, behold, God is indeed much-forgiving, a dispenser of grace.” (An-Nisaa’ 4:23)
Allah Almighty knows best.
Source: www.askthescholar.com