Thanks for your response
We work online with Just Answer as and when we can - as most of us are running accountancy business or work without that field.
The fact is you are still an employee and with all the information given if the brother will not employ your boss, your boss is certainly still employing you (even if within a new set up) as he pays your salary and therefore must take responsibility for your tax and National Insurance deductions, along with allocating annual leave to you.
This is LAW regardless of what the brother or your boss want and at this stage they are both in breach of employment stats legislation - link here for your information. (this offers basic advise but let me know if you want more detailed access to legislation)
However you are left between a rock and a hard place, you cannot make them adhere to law - and I imagine at this stage this job is better than nothing, but you choices are this
10 Write a formal letter to your boss, stating that you understand that the brother does not want to employ you - but that could your old boss not employ you, and as he is taking tax and National Insurance off you pay as you continue just to get thew sale net pay - could he provide you with evidence of the deductions made in the form of payslips and end of year P60
OR you report them to HMRC and let HMRC handle matters
IF either scenario leads to your job ceasing them you can report them to ACAS who are the employment legislation specialists who can offer you guidance as to taking these two individuals to tribunal as they are not only cheating you out of your rights but I would imagine not paying your deductions over to HMRC or the National Insurance office, and I would advsie against letting this continue.
Let me know if you require any furtehr assistance of contact details to report them to HMRC