Feeling Conflicted

So me and my husband have been married 12 years, together 14 years. We're each other's best friend, or at least that's how I feel. Anyways, I'm an only child, and he has two amazing sisters who he's close with, which I feel is great considering the rest of his family could care less he exists. But his one sister is here visiting this weekend to visit our new beautiful little girl. We all get along, there's no drama there. But my husband and sister were talking, and he mentions to me "oh I didn't tell you this but I told Cassie (his sister)". Normally it wouldn't bother me because the thing he didn't tell me involves his family drama, which I stay away from. But my postpartum hormones make me feel excluded, like he can talk to her about everything and not me. Which I guess is fine, I don't know I just feel conflicted right now and may be it's just me being jealous because I don't have siblings. Just needed to vent this out because he doesn't need to hear me bitch about something so trivial.