Could you tell me what's the chances of kidney cancer coming in your kidney but only this time in both?

Rare. Bilateral kidney cancers at the same time are rare, perhaps ~2% of the time. Though this rate increases with certain genetic disorders.
Sometimes. Sometimes kidney tumors can occur in both kidneys. Often the second tumor is not related to the first (not recurrence or metastasis). In some cases, this is a random occurrence (called "sporadic"); however, sometimes multiple kidney tumors can be the result of an inherited (family) condition. Having long-term medical kidney disease can also predispose patients to develop more than one kidney tumor.