Hmmm...actually there may be a way. If you gave your DBIL the money to purchase the property, then he transferred ownership to you, he may not have to pay back the discount:
"You can apply to buy your council home if:
it?s your only or main home
it?s self-contained
you?re a secure tenant
you?ve had a public sector landlord (eg a council, housing association or NHS trust) for 5 years - it doesn?t have to be 5 years in a row"
"You can make a joint application with:
someone who shares your tenancy
up to 3 family members who?ve lived with you for the past 12 months (even if they don?t share your tenancy)"
"For flats you get a 50% discount if you?ve been a public sector tenant for 5 years. For every extra year you?ve been a public sector tenant, the discount goes up by 2%, up to a maximum of 70% ? or £75,000 (whichever is lower)."
"If you sell your home within 10 years of buying it through Right to Buy, you must first offer it to either:
your old landlord
another social landlord in the area
The property should be sold at the full market price agreed between you and the landlord.
If you can?t agree, a district valuer will say how much your home is worth and set the price. You won?t have to pay for their valuation.
If the landlord doesn?t agree to buy your home within 8 weeks, you can sell it to anyone."
"If you sell your Right to Buy home within 5 years of buying it, you?ll have to pay back some or all of the discount you got.
If you sell within the first year, you?ll have to pay back all of the discount. On top of this, the amount you pay back depends on the value of your home when you sell it. So, if you got a 20% discount, you?ll have to pay back 20% of the selling price.
If you sell after the first year, the total amount you pay back reduces. You pay back:
80% of the discount in the second year
60% of the discount in the third year
40% of the discount in the fourth year
20% of the discount in the fifth year"
"you may not have to pay back the discount if you transfer ownership of your home to a member of your family. You will need to agree this first with your landlord and then get a solicitor to do this for you." www.gov.uk/right-to-buy-buying-your-council-home/help-and-advice