It's never said for sure she has a son, but at least in HF normal, she does get married, have kids, and eventually get a granddaughter. Also, the only reason I even suggested that is that Gudao looks like a male version of Rin in some ways, just as Gudako looks like a female Shirou. If Shirou and Rin had kids together, I hc that those kids would look exactly like Gudao and Gudako.