The story focuses on their relationship, the curse that affects Kyo, and the healing process they undergo together. While the series ends with them happily married, there's no mention of them having children.
However, there are fan theories and interpretations that speculate about the possibility of them having children. Some fans believe that Tohru and Kyo's love would lead to them starting a family, while others imagine that the curse might affect their ability to have children. Ultimately, the decision is up to the creator of the series, Natsuki Takaya.
It's important to note that the Fruits Basket "prelude" manga, which takes place after the main story, also doesn't mention any children.