Luke Bryan has experienced more than his fair share of tragedy. When he was 19, his older brother was killed in a car crash, and in 2007 his sister, Kelly, died of unexplained causes. When her widowed husband passed away in 2014, Luke, 43, and wife Caroline, 40 — who share sons Bo, 11, and Tate, 9 — took in Kelly’s three children, Jordan, 24, Kris, 20, and Til, 17. “We never thought twice about it,” Caroline has said of suddenly becoming parents to teenagers. Now that the blended family of seven has settled into a groove — Luke gives Caroline the credit for keeping them afloat amid all the turmoil — the country singer says he and his college sweetheart have a little more space to enjoy each other’s…