Interaction of two responses in multivariate model in brms

Hi,

I just would like to know whether there is a way to fit an interaction term between two response variables in a multivariate model in brms?

For example:

model_1 <- brm(
mvbind(y1, y2, y1:y2) ~ 1 + x1 + x2 + (1 |p| g1) + (1 |q| g2),
family = “gaussian”, chains = 4, cores = 4,
iter = 2000, warmup = 500, thin = 1
)

Thank you,
Benedikt

I am not sure this makes conceptual sense. Why would you like to fit such a model?