A sigh rasped through her like physical pain. Now she’d made such a dramatic appeal, she’d have to explain it so that he understood how vitally important silence was. ‘Thanks,’ she said quietly. ‘As the relief manager, I think it’s probably best if you have some insight into the story. Zinnia’s getting agitated and uncontrolled. She’s badgering me here at work, as you’ve seen. My family’s non-conventional, as I told you.’

‘Because you have two mums.’ He nodded.

‘Exactly.’ She paused to gather her thoughts, gazing at the table top. This wasn’t a subject she discussed much outside of her family. ‘The trouble is that Zin was conceived by artificial insemination and the anonymous donor gave—’ her cheeks burned ‘—what he gave knowing what he was doing. But my mum, she had an affair and I was conceived. It was only when she ended the relationship that she understood how badly she’d used him. He’d fallen in love with her – he was older and maybe she’d thought he was past all that – and he was gutted. She never told him about me because she saw how unforgivably she’d messed with his life. He had a wife and two sons who were sixteen and twenty-one at the time.’

Isaac was silent, his gaze sympathetic.

She tried to laugh but it emerged brittle and hard. ‘Zin and I are only three months apart. It caused remarks all through school. Though we consider ourselves sisters others considered us stepsisters as we have no blood tie and different surnames. Thing is, there’s no manual on how to be a child from a same-sex relationship. I feel I’ve missed out on half of my family but Zinnia’s the opposite and says she’s got two amazing women as parents and has no need to know her sperm donor.’

For several moments she fell silent. The rain continued to pound and Doggo yawned and stretched out against the radiator. ‘Mum let me think my father was a one-night stand,’ she continued eventually. ‘Then I caught her crying over his obituary and in the emotion of the moment, she told me.’ She shook her head. ‘I felt gutted, cheated, and the only way I could think of making it up to myself was to try and find my half-brothers. It was a compulsion.’

Her eyes prickled and she realised it was a relief to be able to talk about it with someone other than her family. ‘I found my eldest brother straight away via the internet. I know where the other one is but I haven’t met him, his wife or two kids.’

Isaac had apparently become too invested in the story to listen in silence any longer. ‘What did the one you’ve met say to finding out he had a half-sister?’