Before he shattered his C-2 vertebrae while rehearsing for a tour in January, 2012, The Other Side hitmaker admits he wasn't committed to the relationship, but when Sparks dropped everything to be with him he quickly realised it was time to get serious about the romance.
DeRulo explains, "She was awesome. That was the time period when we really got close. Beforehand, I wasn't really looking for a relationship but she literally stopped everything that she was doing and flew down to Miami and took care of me. It was amazing.
"We were just seeing each other (before) and that was cool... but I thought that was amazing."
DeRulo, who spent the best part of a year recovering, now hopes to wed Sparks and make his grandmother's dreams come true.
He tells U.S. news show Access Hollywood Live, "My grandmother is 91 and she says, 'My only wish before I die is to see you and Jordin get married'."
But he adds, "I'm not engaged as of yet, but when the time is right..."