Platy Not Giving Birth

[Fisharecool:)]

I have 3 platys and 3 guppies. 2 female platties, 1 male, 3 female guppies. my male has repetively mated with one female but she has not had any fry? he wouldn't leave her alone so i bought the second female, but he doesn't even notice her. he still trys to mate with the other. why is she not having any? the only ones that had some were the guppies, which were pregnant when i got them.
(oh, and im sure she's female)

 

[5teady_2012]

Give em chance, dont worry, she will be/or will get pregnant.

 

[Fisharecool:)]

ok. i just thought it was kinda strange since she hadn't had any.

 

[LauraFrog]

Some are just infertile due to hybridisation and inbreeding, I have had several that have never produced a brood even given optimum conditions and different males. Also old females often stop having fry, so yours could be old - is she big?