Equal Measures is number three in the Boy Next Door series and is about Dakota and Gabe. They're thrown together when their parents start dating and realise that they like each other probably more than they should given that they could one day be stepbrothers.
Unfortunately for them, they're discovered and Gabe's mother is so horrified she takes her son and runs off to the USA.
They only find each other again once Ross, one of their mates, intervenes...
Equal Measures can be read on its own but is meant to be read as part of the series.