Thank you all for taking time the time to reply. I appreciate your honesty.
I called my sister (she lives in Washington DC) to get another family member's perspective. She said dh should say no.
I see great potential for their relationship. They really do love each other. And they have been a united front against her family (which, honestly, is even more insane than mine...). But without a willingness to accept help or to do whatever it takes to have a successful marriage, there is also a great potential for disaster here.
I really don't know what dh will decide. I have asked him to think about it...and to treat it as if the person asking was not my brother.
Be a light unto the world...not a bug zapper.