Why doesn’t my boyfriends parents know about me?

Found a letter from his dad saying how he hoped my boyfriend and exwife had a good Easter. He spent Easter with me and the whole weekend. I spend every weekend at his house. I have clothes there. I’ve meet his friends and coworkers. Haven’t meet his parents yet. They live out of state. He said he will take me this year. We’ve been seeing each other for a year and 8 months. Officially dating for a year. How do I confront him about this? I know he is still friends with his exwife. He said before that he would show me any messages between them that I wanted to see. Why does his dad thinks that he spent Easter with his exwife? Or am I misinterpreting the letter
Why doesn’t my boyfriends parents know about me?
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