(Might + would have been) Is this sentence correct?
Hello there! How are you?

Is this sentence correct?

“... I wonder what might their reasons would have been.”

Thank you so much in advance.

Question

(Might + would have been)  Is this sentence correct?
Hello there! How are you?

Is this sentence correct?

“... I wonder what might their reasons would have been.”

Thank you so much in advance.

Answer

It's not correct. We cannot use "might" and "would have been" together.

You can have

“... I wonder what their reasons would have been.”
or
“... I wonder what their reasons might have been.”

Answer

1 - Embedded questions use statement word order.

Did Joe sell his car?
I wonder if Joe sold his car.

2 - Might and would are modals.  Use one modal, not two.

I wonder what their reasons might have been.

Your grammar book certainly covers these topics.  If you don't have a grammar book, English Grammar in Use by Murphy is famous.  Paper copies are cheap and a google search will find a PDF.  See units 29 and 50.

Answer

No, the sentence you wrote is not correct. I suggest: I wonder what their reasons might have been.