Here is how we handle our twin calves in our herd. They are tagged different so we know when they come up the chute that the are a twin and what they are a twin to.. bull or heifer. When we have the vet out to bangs our replacement hfrs, if there is a twin to a bull heifer we want to keep, we have the vet palpate her. If she is good, she gets a bangs & goes into the replacement pen. If she is not, she goes into the pen with the rest of the feeder heifers. However, if I were thinking about keeping that heifer for a show calf, I'd have her checked a lot earlier to save us spending a lot of time on something that is going nowhere.
This year, we had a nice set of AI sired twins. This cow is an older cow who never has heifers. The bull, we castrated early. The heifer was really something but she's a free martin. That one hurt. Upside to the story is that the steer calf is a pretty nice steer that my son will show as his first steer project.