NEED ADVICE HELP🥰

Hey ladies. So recently my boyfriend had a party at his house. I was there of course. It was small. However I noticed this couple there. He did not introduce me to them, I never said anything however the whole time I was wondering, who are they? Well come to find out the couple, is his exes sister. So now I’m like why would you invite your ex’s sister and her boyfriend? The thing is, he never even introduced me to them. So it has me wondering. Over all he’s a good man, posts me, respects me, treats me well. But he is so secretive about his past. Especially his last relationship. How should I feel about this situation?