Sleepless nights.

Anyone else babies all of a sudden not sleeping so well. My son will be 3 months on the first and he slept so good at month 2 up until a few nights ago. He would sleep from 830 to 2 and than till 5. And than again but usually my daughger was up by 8 and I'd be up. Now all of a sudden he wants to be up till 10- 12 pm and will be up every 2 ish hours. I know its kinda normal but are we not letting baby sleep after a certain time and how are u getting them to want to sleep at bedtime. Should I wake him up earlier? Because I have noticed he's sleeping later in the morning than before. But I didn't change anything he did himself.