"i should have kicked it with your cousin" is a line from Modesto Is Not That Sweet. This line would normally just mean the narrator was hanging out with his relatives, but due to the previous usage it could mean he is making out with or sleeping with the cousins of his girlfriend, or possibly as a euphemism for simply getting up to promiscuous mischief.
On a fourth level, Craig Finn could mean he was writing the song Modesto... and other songs from Almost Killed Me at the time the incident took place, similar to when songwriters say they were "out riding fences", meaning writing a ballad or a country song as a reference to "Desperado" by The Eagles.
from Hot Soft Light