Our nephew is getting married the Sunday before Tisha B’Av. Even though one is not supposed to get married then, they are non-observant Jews who don’t know better. My nephews and nieces are mostly intermarried and I have been at odds all these years with my siblings for not attending any of their children's weddings. This is the first biological nephew or niece of mine who is marrying a Jew, and I have long promised that if any of them would marry a Jew, I would attend. I really do need to attend in order to keep my promise and maintain harmony with my siblings, even though it is a 9-days violation. What would you suggest I do when at the wedding?