Thank you for your question..
Your gain is the difference between the price in 1996 and the net sale proceeds now.
If you have not lived in that house as your main residence at all, then the whole gain is subject to CGT after allowing for gains allowance of £11,100 for each owner.
CGT rate applicable is 18%, 28% or a combination of both if it is a second home for you and your brother.
I hope this is helpful and answers your question.
If you have any other questions, please ask me before you rate my service – I’ll be happy to respond.