Riddhi and Siddhi were only two wives of Lord Ganesha. Here is a story about the marriage of Lord Ganesha.
On hearing Ganesha's intelligent words, Shiva and Parvati were pleased and at once decided to celebrate His marriage first. Prajapati Vishwaroopa's two beautiful daughters, one called Riddhi and the other called Siddhi, were selected to marry Lord Ganesha. The divine sculptor Vishwakarma made all the arrangements for the marriage by constructing a beautiful marriage hall. Lord Shiva and Parvati celebrated the marriage of Ganesha to Riddhi and Siddhi, who bore Him two beautiful sons named Labha and Kshema respectively.
Here is a mention in shiv purana about Riddhi and Siddhi the two wives of lord ganesha and there sons too.
Even half way through the full circle of the World, Sage Narada intercepted Kartikeya and conveyed that Ganesha’s wedding with Siddhi and Riddhi was in progress already (they were blessed with two sons Kshema and Labha eventually)
so a few things we get here
- Lord Ganesha have only two wives Riddhi and Siddhi
- Riddhi and Siddhi were daughter of Prajapati Vishwaroopa
- This story is mentioned in Shiv Purana.