User blog comment:Leland Davis/What I have read so far in "Trouble Twins"/@comment-4449950-20160523014720/@comment-2125188-20160525092138

Or you could read Carry's original comment where she quoted the twins saying "Because our dad is scarier. He scares people without even speaking." Clearly, Gajeel is alive in the future based on this novel. Although, Gajeel and Levy weren't stated to be the parents, but heavily implied.

Don't think this novel is absolutely 100% canon, but doubt Mashima would let something like this slide if it wasn't canon.