Just found a copy of this recently discovered (1997, in Florence)
improving gem by Mary Shelley.
It touches on loss of original family, surrogate families, infant
kidnapping, name change and identity loss, nature v. nurture (though
this childrens' story differs from 'Frankenstein' in that innate
goodness prevails over ill-treatment)
Even though there's a conventionally happy ending, the story is
suffused with melancholy. In her introduction Claire Tomalin writes,
'The theme is loss: parents lose their child and seek him year after
year; another woman longs for a child so badly that she steals him;
the child loses his identity when he changes his name and is passed
through the hands of three sets of parents, his natural ones, his
forster-mother and the old couple who take him in and then die,
leaving him alone and unprotected.'

A review can be found at :

http://www.erudit.org/revue/ron/1999/v/n15/005868ar.html