Sim lives in household but won't let me play as him

So I downloaded 3 sims from the gallery and made a household with them, 2 of them were playable but the 3rd one was in the house and lived there and wouldn't let me play as him and didn't show him in the house. But when I loaded the household on my gallery it showed him there. So I tried to add him back, but it wouldn't let me. I even tried adding him to my own gallery but it just won't let me. What should I do?