I wanted to ask:
Say for example
-Khadijah and Muhammad are married and have a son Yusuf.
-Sulaimaan and Ammaarah are married and have a daughter Ayesha.
Yusuf married Ayesha.
In the meantime Muhammad passes away/ divorces Khadijah and Ammaarah is divorced/passes away.
Will it be permissible for Sulaimaan and Khadijah to get married keeping in mind that their respective sons and daughter are married to each other.
In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
It is permissible for one to marry his daughter in law’s mother and vice versa. 
In the enquired scenario, Sulaiman and Khadija can get married to each other.
And Allah Ta’āla Knows Best
Mufti Muhammad I.V Patel
Checked and Approved by
Mufti Nabeel Valli
Darul Iftaa Mahmudiyyah
الأصل للشيباني ط قطر (10/ 185)
ولا بأس بأن يتزوج الرجل المرأة، ويتزوج ابنه ابنتها أو أمها أو أختها أو عمتها أو خالتها أو ذات رحم محرم منها
فتاوی دار العلوم دیوبند جلد7 صفحہ199