@ethan.payne will try that, I think we can implement this as a feature for N likelihoods in the future

@gregory.ashton This worked with a minor change:

class JointLikelihood(tupak.core.likelihood.Likelihood):
    def __init__(self, likelihoodA, likelihoodB):
        self.likelihoodA = likelihoodA 
        self.likelihoodB = likelihoodB
        self.parameters = self.likelihoodA.parameters
        self.parameters.update(self.likelihoodB.parameters)

    def log_likelihood(self):
        self.likelihoodA.parameters.update(self.parameters)
        self.likelihoodB.parameters.update(self.parameters)
        return self.likelihoodA.log_likelihood() + self.likelihoodB.log_likelihood()

I'll make a merge request!