"叔仔黑口黑面" --- What is their relationship like? May be your 叔仔 has a lot of arguments with your 99 about the wedding, so he acted like that to reflect his dissatisfaction!!!
I didn't say 叔仔 is right because it's his wedding & he should be responsible for it. But if he didn't do it (e.g. to against your 99, or for other reasons etc.), at least your 99 should pay for him first because it is her son's wedding !