At British Airways, there is a buddy/married roster system in place that seems to work very well.
You always get the same trips as your roster buddy APART from when you're on standby. You may/will(??) be rostered standby together BUT if only one of you is needed, that will throw your roster off a bit and it might take a few trips to get back in-line.
As a condition of being allowed to operate on married rosters, you need to give up one set of your staff travel concessions (i.e. one of your families won't be able to use Staff Travel).