Do you do pardah from the son in law in iddah?
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the name of Allah, the Most Gracious, the Most Merciful
Purdah and Hijab are done with those individuals who you cannot marry. Once a man marries a woman, her usūl (mother, grandmother and ancestors) and furū’ (children, grandchildren and progeny) become haram upon him forever. This is why he can never marry the ancestors or progeny of his wife.
In other words, you do not have to do purdah from your son in law since he can never marry you.
Only Allah knows best
Written by Maulana Shadman Ahmed
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Marghinānī, Abū al-Hasan Burhān al-Dīn ’Alī b. Abī Bakr b. ’Abd al-Jalīl al-Farghānī al-. al-Hidāyah fī sharḥ bidāyah al-Mubtadī. Vol. 1. Pg. 186. Beirut, Lebanon: Dār `Iḥyā al-Turāth al-’Arabiyyah, 593H.
al-Fatāwā al-Ḥindiyyah. Vol. 1. Pg. 274. Dār al-Fikr, 1310H.