my sisters baby boy 3 months old .not taking mother's milk for last two days...he is crying while feeding...but when he is sleeping he suck well for hardly 5 mint ... otherwise crying continuously...n. not suck ...cry while attached to nipples

A. Hello good evening !! At this stage 3-5 months rejecting feed from one side or completely is normal as they habituated or set to sleep routine they know their hunger so take 5-10 minutes feed sleeps at a stretch. If the baby is gaining weight ,sleeping well,peeing 7-8 times a day then no worries.