If the property is in the name of you, your brother and your sister, all of you need to sign a Disposition (title deed) transferring ownership to the purchaser. If your brother isn't easily available to do this then you might want to get the lawyer to email him a power of attorney in your favour to sign and send back so that you can sign for him at the relevant time. Happy to discuss further. I hope that helps. Please leave a positive rating so that I am credited for my time.