If it can fit into your schedule try the flavor of biphasic sleep where you go to bed with everyone (or even a little early) then wake up 4 hours later for 2 hours or so max, then sleep another 4. It will give you your alone time, with a motivator to get to bed earlier as that is now a prerequisite. It has been proposed that this is closer to the "natural" human sleep cycle that people used before ubiquitous artificial light.