The relationship
The Early Years
It's unclear as to when, where and how the two met, but for at least a few years before season one, Logan and Duncan were close friends. Logan dated Lilly, Duncan's sister while Duncan dated Veronica, his sister's best friend. The four of them did virtually everything together, up until a secret and death tore the four of them apart. Lilly's death took a toll on Duncan and his personality. Though they remained friends, there was a slight distance between them.
Season One
coming soon
Season Two
During the summer, Logan and Veronica continuted their relationship, though it was strained due in part to Logan's trial and tensions at an all time high between the 09ers and the PCHers. Duncan decided to cut summer at Napa short and returned to Neptune with one thing on his mind, to get Veronica back. Ultimatly, Veronica and Logan broke up, and Veronica sought refuge with Duncan. Tensions between Logan and Ducan escalated when Logan made a quip about Veronica. This lead to a schoolboy fight in the hallway and Logan breaking in the Nurse's office.
With everything out in the open, the air finally cleared, the two make with virtual violence and make amends. After a fire destroyed his home, Logan moved into the Neptune Grand with Duncan. The two remained close until Duncan fled the US with is daughter.