"do incest relationships work"
To answer that, one must describe what means for a relationship to "work."
For some people, a relationship only "works" if it is heterosexual and always monogamous, involves religious and civilly affirmed marriage, produces (or at least raises) children, and lasts until one of the spouses dies.
For me, a relationship "works" if you are, as a whole and excluding artificial negatives like prosecution and discrimination, better off as a result of having been in the relationship. What makes you "better off" is up to you. It could be strictly that you enjoyed this person's company, but it could also be that you had children together, or helped each other grow as people, or made new friends through the other person, or helped each other's careers, or... well, any number of things. A relationship doesn't have to last until death to leave you better off.
A sure sign a relationship isn't working is if one of you is abusing the other, or you're abusing each other.
Over the years, I've been fortunate enough to talk with countless people who've been involved in consanguinamory. A few of them have even been generous enough to be interviewed. For most of the people I've talked with, the relationships have worked. If the consanguinamory is in the past, they have fond memories of the great times that were shared and the emotional growth they had as a result, even the sexual confidence they developed. For many, the relationship continues and provides times of unmatched bliss and intense intimacy, even shared parenting that they have found fulfilling.
So yes, they can and do work.
And, by the way, some of them are heterosexual, always monogamous, produce and raise great people, and last until death, and it is an injustice that they are still discriminated against under the law.