A story doing the rounds this week — a woman whose parents refused her a £10,000 loan while quietly bankrolling her brother's house purchase — might read as a domestic squabble. For the UK property market, it is anything but trivial. The so-called Bank of Mum and Dad has become the single largest source of deposit funding for first-time buyers in Britain, and the uneven, often opaque way that families distribute this capital is now a structural feature of who gets on the housing ladder, where, and when.