It seems very complicated. To make sure I understand properly, and for ease, let us assume the house is worth �100,000.
He owns 60% but wishes to live in it, so must pay his sister �20,000 lump sum and rent of �1560 per year. The rent does make up 20%. How many years would he have to pay? What happens if he changes his mind after 12 months and wants to sell? Does he get the �20,000 back?
Your daughter already has half of her 20% share - if she were paid another �40000 she would have 60%.
Is this what you mean? What do you hope to achieve?