Is my daughters boyfriend and his friend "just boys being boys" or is it... More

I know I shouldn't be speculating on another child's sexuality but I just don't want my daughter getting hurt. Especially since he's coming for Christmas. She's 16 and has her first boyfriend. Now she's really smart so she's skipped a trade so she's a Junior while her boyfriend is 2 grades behind her. He's a freshman and 15. I am aid with special Ed students at the high school and my kiddo has a class with her boyfriend. Her boyfriend has a best friend he's close to. Before winter break something happened that's been on my mind. I was helping my kiddo try to leave class but he wanted to stay because he was overwhelmed. I could see and hear my daughters boyfriend talking to his best friend. Tell me if this conversation sounds like "friends" or more than friends.

Daughters BF:Are you wearing underwear

Best friend: Yeah

DBF: Okay. I'm not. I have Gym today and forgot

BF: How did you forget underwear?

DBF: I just did. And I have to change in Gym! Let me borrow your underwear!"

BF: What?!

DBF: Dude. I have to borrow your underwear! I'm wearing nothing and have gym

BF: Fine. Just give it back after lunch.

My ex husband thinks I'm making nothing into something and they're just boys being boys and at the most need a hygiene talk. I can't think of a single male who shared his underwear with another male. That just doesn't seem normal and I again just want to protect my daughter from getting hurt.