We've gone through several variations of one of them preferring one of us for a <span style = 'background-color: #dae8f4'>period</span>
of time. I think it is completely normal. I think extreme separation anxiety, i.e. if you leave for a short period
of time and the child is inconsolable in your absence, may merit more attention, though. I am sure it depends on the child, but I've always found with my children that if I tell them I'm going out, and when I'll be back (I've even given them clocks, timers etc.