I will throw in my 2 cents on this being a bull that has a 'must requirement' that the cuck must suck me as well.
Depending on how and where we met, on an internet site like this or aff or what have you, I try to make it clear on my profile that it is a requirement as I have done here. If I don't then I seek out for couples where his sexuality is listed as bi or bi curious. If a couple with a straight male contacts me, I ask straight away if that is something they are into.
If I meet a couple off the internet where there isn't really any opportunity to know what they are into before hand like one time at Hedo in Jamaica. I try to gauge them by asking probing questions that might suggest they might be into it. Responses like 'we are very or pretty openminded', 'We are up for most things' or if they made it clear that he is submissive gives me the green light to give an outright command that he suck my cock. Has worked everytime.
I have also had situations where the cuck gave indications during me fucking the wife, like getting too close or looking at my cock without touching, in ways that that would be deemed too close for comfort by a bull that is not open to it, in that case I just order him to.
Generally. I do not meet or play with couples where the cuck won't suck my cock. I always want to know they are game before hitting the bedroom if they are not or I am not sure. I generally don't.