See Brian lawson's transcribed wills.
Timothy Crebbin 1745 LDS film 0106218.
He mentions children Isabel, Timothy, Thomas & John but no wife, nor Katherine, a daughter.

Two children, Katherine (1715) & Thomas (1718) show up in the IGI taken from the Parish Records. Timothy, John & Isabel are on the IGI but from some other (reliable?)source.
Rushen parish & birth records are pretty sketchy before 1720.
My guess is that, based on the birthdates of their children, they married before 1714 when they were in their twenties.
Good luck.