Three threads about Stepchildren on Mumsnet have stuck in my mind because I found them sad and upsetting and on the basis if them I do think that LOTS of stepchildren, possibly the majority, get a raw deal, though of course not all
Thread One :
Poster wanted to place large canvas photos of ONLY her OWN children in the living room and have a small one of her stepchild elsewhere.
Her argument was that why shouldn't she have photos of HER OWN children in HER OWN home.
Seemed oblivious, absolutely oblivious, to the fact the other child was her DH's OWN child and it was also THEIR home and their child's.
Thread was deleted
Thread(s) Two :
Poster came on repeatedly under different usernames and was caught out for strenuously insisting it would be ok for her SDC to share a strip of the landing as "their bedroom" rather than give them a bedroom.
Was resoundedly handed their arse on every thread.
Thread Three :
Thread was deleted after the poster got outed. Poster's husband was in a convoluted car share agreement with his daughters half siblings Dad and had to do ONE long return journey once a month to see his kid.
Poster was pregnant and wanted all contact with his existing child to cease outside of school summer holidays so he could "focus on our own little family" 
Poster was rightly ripped apart
But I felt for all those children and remembered all those threads even though they are long gone.
So many people should not get into a relationship with someone with kids. It is the kids that suffer.