Exactly. Can’t tell for sure and when a man and woman live together in such stressful situations, cheating could be a possibility. Your mum may have found solace in him.
Came here from r/AskIndianMen , I do not doubt for a moment that your paternal family is very toxic and has a lot of issues but if there’s a chance that your mom was cheating on your dad whilst not divorced, that’d turn messy in court. Plus that’s not very ethical. Neither is what your dad/dadi did.