Change in toddler/ siblings while pregnant?

Chrissy
Hi ladies! Has anyone noticed a change in your toddlers/ other siblings while you've become pregnant? I have a 5 year old boy and he doesn't know I'm expecting yet but he has had such a change in his attitude. He seems to be way more attached and also (hate to say it) but has become quite the crybaby about things. It's almost like he senses it lol his "only child" days coming to an end. 
Has this happened to anyone else? Not concerned, just want thoughts. I've already heard some family myths that depending on how children react, it can hint the gender of the baby in our belly. I think it's a bit odd but who knows. I'd love to hear any stories if y'all have any. 
Safe pregnancy y'all 😊