Question Summary:
Can a widow re-marry without having any witnesses?

Question Detail:

is it true that a widow can re-marry without witnesses.
the man she intends to marry is already married. both are sunni muslims.

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
It is a prerequisite for the validity of a marriage to have two witnesses present to witness the exchange of the proposal and acceptance of the marriage[1]. If there are no two witnesses, the marriage will be invalid. Accordingly, the widow cannot marry without two witnesses witnessing the marriage.
 
 
And Allah Ta’āla Knows Best
Immad Bin Arshad
Student Darul Iftaa
California, USA
Checked and Approved by,
Mufti Ebrahim Desai.
www.daruliftaa.net