Of course they won't breed. There is only one way through which gender less Pokemon like Starmie can breed, and that's with Ditto. No matter how hard you try from there, Starmie won't breed with anything else, despite being in same Egg Group.
If you want a Tentacruel with Rapid Spin though, there are a few ways:
Breed a male Squirtle (with Rapid Spin, it gets that at level 19) with a female Kabuto, you must aim for a male Kabuto with Rapid Spin.
Breed this offspring Kabuto with a female Tentacool/Tentacruel, and voila! The offspring Tentacool should have Rapid Spin.
Hope I helped!