Split of house ownership

[NellieBertram]

I'm asking for a friend who's buying a house with their partner, they're not married.

I understand they will be "tenants in common" rather than "joint owners" so need to decide on a fair split. Friend has asked my opinion.

The house is worth £200k.
They have a joint mortgage for £100k.
My friend has a deposit saved up of £25k.
Friend's family member is lending them the other £75k.

Friend wants the split of ownership to be 25% to partner, 75% to friend. The loan will be repaid to the family member by friend when the house is sold.

Does this seem fair to everyone?

So friend and their family are paying 50% upfront and the rest is on a shared mortgage.

If they are going to be sharing mortgage payments and bills equally, then yes, the friend will own 75% and the partner 25%.

Unless they subsequently marry or have children. Then it all changes.

Yes, they won't get married although they do have children together.