I found associations for Foerster, Forrest and Forrester. So, there is a good chance. Very possible.
I can tell you that the most prominent Rothschild/Sinclair marriage I have found was that of Jacob Rothschild and Serena Mary Dunn. She was the daughter of Dunn (father) and St. Clair-Erstkine (mother). I'm also looking into the Sinclair/Guinness connection.