Can the payor spouse argue that the custodial spouse has a legal duty to support the child other than the child of the marriage?

The appellant submits: The payor spouse may argue "undue hardship". Section (2) (d) of the Guidelines contemplates that one of the circumstances that may cause undue hardship is that "the spouse has a legal duty to support a child, other than a child of the marriage". However s. 10 indicates that the discretion to award a lesser amount of support only exists where hardship is "undue" and even then a lesser amount should not be ordered if the payor spouse has a higher standard of living than the custodial spouse. Von Sturmer v. Von Sturmer, [1998] B.C.J. No. 1046; (1998), 81 A.C.W.S. (3d) 113 (B.C.S.C.).