awww...sweet sweet Minion!! Bless his little kitty heart!

My only guess would be he's become like that because he's afraid of being left behind again, or it's something related to his past. Maybe he was really outgoing (which is when and how he got your attention) at first, but now that he landed you for his new family...he's become more afraid of people other than you and Dan. He might feel insecure.
It's hard to tell when behaviors like this crop up, because we don't really know what happened to animals before we rescued them. It's possible that a visitor came and took Minion away and dumped him, or maybe he was simply left behind. It's hard to tell...
My suggestion would be to have your guests get the opportunity to give Minion treats when they come in, so he associates good things with visitors. Have the guests sit in one place and remain calm, and let him come to them.
What a cutie he is! I sure hope this is something he can work through! Give him extra scritchies and treats for me!

**hugs**