I had 2 joint accounts with my sister, who has transfered all the money into her and her husband and closed the account. She has admitted that the money is all mine in a email and that her husband will pay me back. However now she has stopped emailing me and does not pickup her phone, I can also prove that all the money is legal and was transfered from my own accounts and the only reason I had her on the account is because I am single and have no benificiaries,
It appears that you have a legal claim against your sister and bother-in-law.