Father’s Day is this weekend, and in honor of the big day, we’re looking at a kind of father that doesn’t always get a lot of attention: single dads. One recent calculation using 2010 Census data found the number of single father families nationwide jumped 27 percent in the past decade and nearly doubled since 1990. Here to give us insights into these shifts is Roberta Coles, chair of Social & Cultural Sciences at Marquette University and author of “The Best Kept Secret: Single Black Fathers.”   Alexi Peck is a single father of a 12-year-old girl, he shares custody with his wife.