Early on in Rivers of London, after the aversion of Infant Immortality, Leslie comes into Peter's room, strips to her underwear and the two of them sleep spooning after the horrible events before. It's absolutely adorable and shows just how much the two of them care for each other.
In Whispers Under Ground, when Peter is hospitalized, Leslie is sitting next to his bed when he wakes up. Nightingale also comes to visit and just barely refrains from hugging him, because that would be gay.
In the same book, after Nightingale and Peter exchange Christmas gifts (a watch that magic won't fry for Peter and a cell phone for Nightingale), Peter invites Nightingale over for Christmas dinner. Nightingale says he can't, unfortunately, because he needs to stay with Molly on Christmas.
In Foxglove Summer, Nicky's mother brings the girl whom Peter and Dominic retrieved to the faeries to attempt to trade her for her own daughter. Peter then informs her that the girl she's offering to trade away is her biological daughter, who'd been swapped as an infant for the changeling she's been raising for ten years ... and Victoria still insists upon making the trade, because all genetics aside, she wants her Nicky back, i.e. the little girl she's been bringing up. Great vindication for adoptive parents, there.