To be bought out, my options?

Basically, I bought a house with my brother in which we live in together. Him and his gf have decided they would like the house to themselves and are offering to buy me out of the property. I saw my personal banker and they said if they do this, there is literally no way I will be able to buy again on a single income. We could possibly subdivide the section but it doesn't sound like my brother is very keen on that. I'm not being forced out, but I don't feel I have much of a choice.

Does she have to buy into half of the property? Or only my part of the deposit I made?

I'm not really sure what my rights are in this situation or if anyone has any advice?

Thank vou.