Groom wanted his twin sister as Best Woman. Bride and MOB said that would be weird. Groom was insistent. Then bride, without asking groom asked the sister to be a bridesmaid so groom thought it was a decent compromise and went with it.
The sister was told the girls were buying their own dresses, and doing their own hair and make up, which she was fine with. She arrived the morning of the wedding to discover the other two bridesmaids had been and had their hair and makeup done (she had asked several times the plans and had been told they were 100% doing their own). The other two bridesmaids also had matching shoes and matching jewellery.
When the bridesmaids arrived at the church groom instantly noticed the jewellery, but his sister told him not to worry about it.
At the photos he overheard the other two bridesmaids talking about the three of them getting their hair and make up done and realised they meant them and the bride. He and the bride had a massive blow up, came out at that point that they had budgeted for the three dresses and shoes but his sister's budget had paid for the other girls hair and make up.
The bride was in tears most of the reception. In the groom's speech he was reading like he was reading a menu, apart from the bit when he thanked his mum and sister for their support.
A load of other things came out after the wedding - his mum had paid for all of the flowers yet she wasn't given a corsage despite the MOB, MOB's three sisters and the mothers of the other two bridesmaids being given one. His other sister (much older than him) had given them £5k toward their wedding and she was sat on a table with her SIL's workmates due to "awkward numbers on the family tables" and since she was single (she was widowed) it was easier to shift her.
The couple split up within days of the wedding.