no. your babies may not do that, but it is considered normal.

one of my four children slept 18 hours per day, in three 6-hour sessions, for many months.

The chart is slightly misleading, in the sense that the ranges shown are more like the very strong average sleeping patterns across babies. It doesn't mean that none of them woke up for a quick feed. But even without a feed, sleeping from 11pm-7am, is certainly not abnormal.

16 hours of sleep also falls within normal for a 15 week old baby for most sources I've seen, so I'm not sure why you'd be worried? I had a look, and my daughter was around 15-16 hours. No big naps during the day, but she slept 7pm-6am maybe waking twice for feeding.

Every time they go to sleep, they eventually wake up !