Little Sister troublesWatch this thread
However, I can see elements of control and manipulation coming from my sister. It’s really concerning and I have tried to warn her and talk to her about it (We witnessed this behaviour with our mums relationship with men).
Any advice/tips? Anything I can really try to do?
You should talk to him and see how he feels about it, he should know that you realise what your sister is like so he'll feel at ease.
In the end its his decision, maybe if he decides to break up with her she'll learn from it.
sometimes you have to do things the hard way in order to do the right thing