Re: True sincerity from heart & Soul
Brother if you read "Hayat-us-Suhaba" you would realize that even alot more amazing incidents than the one I mentioned were not only in books but in REAL life as well. Though if we consider present age, than you are right, such cases might be rare, but we can't say they don't exist.
About the first example, I have yet to see a step father or step mother in present age doing justice among their "own" children and other children. There might be cases of sincerity of step parents but may be 1 % (in my understanding, I might be wrong). He didn't re-marry because he and his wife promised to each other that if anyone of them died, the other wouldn't re-marry. (probably for the better future of their children and saving them from inferiority complex) :)