Waking at same time every night 2am and 4am -WTD?

AlXaNgEl

K consistently wakes up around 2am and 4 am every night like clockwork.  We don't let her cry very much cause DS room is right next door.  DS is a light sleeper and the last thing I need is to have both of them awake.  So usually when we hear a peep out of K we go and pick her up.  I'm thinking this has became a habit for her now and she wakes cause she know we'll go in there.  Do we just stop going in there and let her cry, even though DS will probably wake up?  Thing is if DS wakes up and K is crying he'll probably never go back to sleep until she stops.  Any advice?