LAWRENCE — An annual youth membership at the Dufferin Clark Community Center runs $15 these days, which means even now it would cost Mitchell Wiggins just $45 a year to keep his boys happy.Sure, his three kids — Mitchell Jr. the oldest, Nick the middle son, Andrew the youngest of the bunch — had other interests growing up. But it was the basketball court that lured them in like a magnet, from an early age each trying to follow in their father’s footsteps.“They all three had a dream to follow what I did,” said Wiggins, who played for several years in the NBA before finishing his career overseas. “They grew up in the gym, and mom and dad are athletes, so a lot of things came naturally for them.“But they pushed each other, too.”The three precocious Wiggins boys, bound by brotherhood and basketball, already have pushed each other a long way from those simpler days at the rec center just down the street.By now, everybody is familiar with Andrew, the consensus No.