We know both ladies have had children by dudes of course, but since Irene sees the future well maybe she saw what a good hero Rogue would be in the future and told Mystique to turn into a man to get her pregnant. This would make Nightcrawler and Rogue siblings by blood. And it would be what Claremont intended for Nightcrawler, but it’s since been established Raven is his mom and Azazel the dad. Plus I don’t think Irene and Raven what let a stranger raise a child together, so this story doesn’t fit Kurt. But it does Anna.