K.H.
Hi T.
Sounds like he is growing again and needs more food, & drink. Maybe you can do that with more food in the day, but maybe not.
Are you complaining because he wakes, because you must get up, or because you think he should sleep 12 hours and that should remain consistent?
My children never slept all night, not the big kids--those whose weight and height were equal, and not the little kids -- those whose weight were under the charts.
In fact, the oldest slept 12 hours plus 2 hour nap-- he's 37 now and still needs 10-12 hours sleep a night. Our younger son was nothing like him. I thought they would be. Oooops Our younger son climbed out of the crib at 6 months and walked at 7 months, and slept about 2 hours in 24 from the time he was about a year old.
MD said nothing wrong, and today he is a lawyer with son of his own and his wife is trilled that he doesn't require a lot of sleep because he can spend the night with the baby, as he still only requires about 2 hours in 24. Our twins--one sleeps about 8 hours and always has, and the other about 4. When I told the MD, I had always said if I had another who only slept 2 hours in 24 I would keep pounding the door of MD office to find out problem. Guess what "he said she's sleeping 4, that is double what he slept"
Today she is at college and loves it because there are things to do when she is not sleeping. The other twin is commuting this year staying I need my sleep.
They are all different and those differences start showing up early.
My advice -- don't compare, don't read what average kids do, don't make assumptions. Make sure they are not hungry, make sure they are comfortable, & see what they are doing and work with that.
Since I am old enough to be your mom, I usually say talk to her she may have lots of stories to tell about you and your siblings that you never heard. MIL's like to tell stories too.
God bless you and your lovely family
K. SAHM married 38 years with adult kids--37, coach; 32 lawyer, married with son; twins 18, in college; one majoring in art, and the other journalism.