His jealous

When we arrived to my sisters place last Saturday, my son was always telling me that he was jealous. I don’t know if he understands that word jealous because when I ask him he did not answer like he knew. He kept saying that and I think he was only saying it to make his auntie laugh. He kept saying it when we were busy decorating my sis new tree. He knew that his auntie was crying and I asked her why, but she not answer. When she was chatting my brother, he was also teasing her when he saw her at the web cam.