My brother and I have always been close; he is two years younger than I am. Although I am married, he and I have done thinkgs together like go out to eat & shopping on a fairly regular basis. My husband doesn't mind.
Eighteen months ago my brother met a woman online via a social networking site. This is the fifth woman that he has fallen in love with online. In all five cases he has conversed with the women over the telephone (conversations sometimes lasting hours). He made arrangements to meet one of the women which fell apart at the last minute (she was lying about her name/ marital status/age). He drove 1,500 miles to meet another and spent a week with her.
My brother has made some choices that I would not have been comfortable with, but I do understand that he wants someone to share his life with.
Of the first four women, three are bipolar, and all have lied about various things. When my brother met the fifth woman it came to light that she had been lying about her age... by 17 years, which makes her fifteen years older than he is. This isn't a big deal to any family members other than the fact that she lied; and that wouldn't be bad except that she seems to lie about lots of things. Where she was born, her parents names, her name, where she lived... these are all things that she is inconsistent about.
However, my brother is the one that has to live with her, not me. My problem comes from the fact that he is not allowed to spend time with anyone other than him. Friends, siblings, mother... no one.
He brought her back with him after going to meet her, a 2,000 mile journey. I tried to be friendly & asked her to join me when I was going places. I thought she might like to have someone show her the area. Every attempt was rebuffed.
She hasn't worked since she arrived, & hasn't even attempted to get a job. (I heard this from my mother who he does see once every month or so... they live next door to each other) He is partially unemployed.
The only times that I see my brother now are when I go to his house which is a short distance away. He used to stop by my house nearly every day; frequently giving me more details than I needed about his life. Now I am treated rather coldly; as if I am a casual acquaintance or even a stranger. His girlfriend won't speak to me & continually posts rants on Facebook about how horribly people are treating her.
I feel as if there is nothing that I can do; the person that I knew before he began meeting these women online is gone & I don't really like the person that he is now.
Is there anything I can do?
I truly feel as if I have lost my brother; my siblings feel the same way. I honestly ca say that I have never said anything negative to either of them about her; not even when she left to meet some other men that she met online and then came back. I just can't understand what the problem is.
My brother says he 'hopes it will all work out' and 'can't understand why we all can't get along' he also recently said that 'getting married might make her feel more secure'.

What are you hoping we can tell you? There is nothing you can do, short of paying a PI to investigate her background for something so horrible that your brother will leave her (and probably never speak to any of you again). I hope your mother isn't helping support him. Let him figure this all out on his own. He has to.

He's his own person... he needs to make his own mistakes and hopefully learn from them. There is no way that she can prevent him from visiting family unless he allows her to do it to him... so, this is his problem to deal with. There's really not much you can do about it.

Thank you for your responses; although I do find it disheartening, I totally agree with both of you. I didn't really think that there was anything that I could do, but posted in the hopes that a fresh and non-biased viewpoint might think of something that I was missing.