When the Crawfords took charge of their niece and nephew they are referred to as children. Mrs. Grant knew and was fond of them when they were children and “her own marriage had been soon followed by the death of their common parent [mother], which left them to the care of a brother of their father” (4). Their father died before their mother—I wonder if he was in the same profession as his brother. Since they were children when their mother passed, I think Mary & Henry’s greatest influences growing up were their aunt and uncle:

In their uncle’s house they had found a kind home. Admiral and Mrs. Crawford, though agreeing in nothing else, were united in affection for these children, or, at least, were no farther adverse in their feelings than that each had their favourite, to whom they showed the greatest fondness of the two. The Admiral delighted in the boy, Mrs. Crawford doted on the girl; and it was the lady’s death which now obliged her protegee, after some months’ further trial at her uncle’s house, to find another home. (4)

I agree Admiral Crawford is derelict in his duty as Mary’s guardian but are you saying Henry has no duty towards his sister when she has been forced out of her home by said guardian? Henry reminds me of John Dashwood of S&S. Like John, Henry has no legal obligation to house his sister but like John I think he has a moral obligation. Henry did not know Mrs. Grant or her husband was willing to take Mary in when he refused his home because Mary only wrote to her sister afterwards. I now think Henry’s willingness “to fetch her away again… whenever she were weary of the place” is irrelevant because had she found life at the parsonage unbearable exactly where was he going to fetch her away to?