I don't think you'll have a risk of cross pollination, and in anycase it'd only effect the seeds of the fruit you grow (and anything you'd try to grow with those seeds), not the fruit itself.

When planting outdoors you should sow quite a few seeds per hill.

However, when starting indoors you should do one seed per cell or hole or however you're starting seeds. Then you can transplant them to a hill later at the desired density.