Cats meowing wakes me up at sunrise! why are they doing this?

My 2 male cats sleep a lot during the day and at night they are more active which is normal. I am usually up until around midnight watching movies and they are in and out of my room. I will wake up to use the bathroom and they usually are asleep in my room with me, one snuggles right up to me, the other on the chair or foot of the bed. Now almost every day around sinrise they will start meowing, this wailing meow almost, sometimes it sounds like sooking, lol It ALWAYS wakes me up and I will turn to see them sitting at the window, trying to peak through the blinds. WHY are they doing this? I am almost 27 weeks pregnant and I feel like they are preping me for the baby waking me up after a few hours sleep, LOL Maybe not really but they never did this until the past 2 months. I joke they are half roosters because its like, when sun hits, or daylight, they start meowing to wake me up. If I ignore them sometimes one or both will come on the bed and meow and i will open my eyes and they are looking at me! its funny though. they are not outdoor cats so i know they arent looking to go outside. One of them, we had when we lived away, and had to leave him in the living room at night because he attacked my bf's feet at night, and close the door, and at daylight he would cry at the bedroom door. he stopped this after I moved home to my parents place and now after a few months him and the male that was here already are both doing it.