Has this actually happened or is it a theoretical question? Who is the man in the house? Is it the Dad?
There is no CGT on a death, so ignore that for a start. There is probably no stamp duty either ( unless certain appropriations).
Then factor in appropriation of the family home for the spouse, if that is what she wants.
If it hasnt happened, then please tell the dad to seek legal advice and get a will made asap. If it has happened, please seek legal advice, lots of possibilities here, depending on the circumstances, disclaimers, family arrangements, agri relief, dwellinghouse relief= really tax advice is very particular to personal circumstances.