My gf and I have decided to have an MFM threesome. We discussed all the pros and cons, how it could potentially affect our relationship, layed all the ground work and ruling of what is and isn’t allowed. etc.

We would prefer to have both males go completely raw. Only issue is that we’re not sure how high the risk is of contracting anything if both males aren’t using any condoms (of course we do know it is safer to use condoms, but this is our first time, so we would like to get the full experience). We decided on asking a friend of mine to join us (not a best friend, so there is a possibility of breaking ties with him once everything is finished, depending on how comfortable we feel afterwards towards him). We’re very sure that he does not have anything, since he isn’t very sexually active, nevertheless we will still require him to go for a test before the threesome.

My question is, if no one involved in the threesome has any kind of infection or std. And both males go raw. How high is the risk of contracting any infection or std? And is it possible to contract an infection or std, if no one involved has one already?