Let $\displaystyle R,S$ be integral domains of characteristic zero. Let $\displaystyle K$ be the minimal field extension containing $\displaystyle \text{Fr}(R)$ and $\displaystyle \text{Fr}(S)$ as subfields. Does there exist an integral domain $\displaystyle T$ such that $\displaystyle K = \text{Fr}(T)$ with $\displaystyle R$ and $\displaystyle S$ are both subrings of $\displaystyle T$?