Baby becomes Super whiny

Hi all, my son just turned 1 year old, a week ago and suddenly became extremely attached to his mother. He is very whiny and would cry when my wife leaves his sight for even brief moments. Also, we are expecting our second child (we tested positive a month ago). Our parents in law shared (could be folks tales) that my son is whiny because he could sense that he is having a sibling soon. Just want to know if anyone encounter something like this?