We also had a set of twins born a few years ago...about a month early. The bull calf was apparently stillborn, at least he was dead when my dad found them. The mother was fighting off the buzzards, and the heifer calf was alive, but she was too small and weak to stand or walk. My dad called me to come help rescue the pair and get them to the barn.
We milked the cow and tubed the calf and then gave her a raw egg, then repeated that again that night at feed time. We didn't expect the calf to live through the night, but she was still alive the next morning. For several days, my dad put the cow in our chute, let the side down, and sat on a bucket with the calf laying over his lap so she could nurse. It was a few days before she could stand on her own, but she did live, and once she got started, she grew really well! We had her in a fattening pen with some freezer beef cattle, expecting her to be a freemartin. She cycled and we decided to see if she would breed...low and behold, she did. She had her first baby this past fall, and she's doing a good job with her. First time we've ever had a heifer that was a twin to a bull and not a freemartin...that we know of anyway.