Why do kids act up most around their mom?

My nephew and niece are the calmest, sweetest, well behaved kids when I watch them with my husband. They listen, they have low energy and laugh and are just delightful lol UNTIL their mom shows up. Anytime they are around their mom or their grandma they become monsters.

Last night my nephews energy changed immediately once she arrived and he was screaming and running around hitting stuff and not listening. He picked up my necklace on the table and said ‘cool aunties necklace’ and pulled it so hard on purpose it snapped and broke. He would have never done that if it was just us!!!!

My niece is only 2 but she turns into a mean baby with her mom and wont let anyone even look at her or she’ll scream bloody murder and cry.

Their mom does have high energy and talks incredibly loud over everyone else and overall just has intense energy. Same goes for their grandma, who they also act up around.

What the heck is going on here? Why do they change so drastically?