DP's parents are celebrating their 50th wedding anniversary. We were told very clearly it is family only and I am not invited (We've been together over 20 years). His brothers are taking their DW and DP; when DP asked, his DM said, 'That's different.' The only difference is I'm not English and they all are. DP has refused to go without me. I think he ought to. I've said I'd take him and bring him back the next day (200m away) but he refuses point blank, says they're insulting us both. AIBU to say his duty to his parents means he ought to go?