Beemail - it's good to hear of your positive experiences of orphanages in India and the good care given to the children. One of the problems (as you say) is that at a certain age the children are moved to another section with different staff, though at least had some connection with the previous carers. This though is a big disruption to their development isn't it in terms of attachment, especially children in the first 3 years of life. Having said this, this is what happens in the UK in day nurseries, children are moved on according to age (which I think is harmful for children under 3) - my own gr/chdr are in a day nursery full time but that is the decision of their parents who both work full time, so there is little I can do. I am not in a position to care for the children myself.
You talk of the strict routine, which is of course the cornerstone of all institutions, be they children, older people, people with LDs etc etc. Everyone gets a drink at the same time, food at the same time, (nappies changed at the same time) if they are babies. Also being kept inside most of the time cannot be a good thing. At least in the day nursery my gr/chrn attend there is a very well equipped outdoor play area, with high quality play material, slides, climbing frames, swings etc etc. Pedal cars and prams etc.
I too know of many situations where there were relatively few problems until adolescence and then problems which have lain dormant emerge, causing great distress to the young people and their families.
I agree the OP's sister's boy needs help, quite urgently, and hope she can access it this - Kewcumber's post sounds helpful in this respect.
So glad your girls were able to visit and meet the carers and see where they used to live - I know how helpful this is, as often I have taken adopted children back to show them in the UK where they were born and where they lived with their birth parents and this gives them some idea at least of their origins.
Thanks for your interesting post, which I'm sure OP found helpful.
Maybe I have too pessimistic a notion of orphanages, and like anything else in life there is great variance between them.