Sister Wives star David Woolley is done talking about wife Christine Brown’s polygamist past — including her ex-husband, Kody Brown, and his other wives. “At first I was OK, but then it got old,” David, 62, says in Us’ exclusive sneak peek from the season 21 premiere, reflecting on constantly discussing Christine’s life. “And it’s repeated.” According to David, 54, their conversations always revolve around exes. “Not just Kody, but all the exes. … It just gets old,” he adds. Christine was spiritually married to Kody, 57, for more than 20 years before they split in November...