Something I thought of while watching "Logan", are the x gene mutants in the Xmen cinematic universe mostly infertile?  The only examples of mutants having children are mutant men with non-mutant women.  ex: Magneto had two kids, but with different non-mutant mothers.

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Even in Logan, the kids were created with in-vitro fertilization (generally used for infertile couples) with non-mutant mothers and mutant fathers.
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