My brother received a text from a number we don't recognize?

My little brother received a text from a number he didn't recognize and responded with "who is this?" Turns out it was a friends boyfriend which is a really really weird coincidence. My friend is saying my little brother texted her boyfriend saying "Who is this?" And she says that her boyfriend never texted my brother. How does this happen!? Neither I nor my brother know this guy or have any contact with him and it's very odd that out of all people that's who my brother apparently received a text from.

If it makes any difference my brother responded with an iMessage using his email address and that's how my friend knew it was him.