Not sure about whether it's more common in TB's, but I owned a twin out of a tb mare by a wb stallion.
Her twin died (could have been saved with a simple operation but lets not go there) but my girl lived on quite healthily. I brought her when she was 4, and other than only being 15.1h when he sire was 17h and her dam 16.1h, she was fine... I thought.
I lost her in a freak paddock accident, her front cannon snapped completely in a compound fracture and all that was left holding her lower leg on was a flap of skin and fur. An immense amount of force would have been required for a horse to get an injury that bad, there wasn't a mark on her from a fall, nothing on the ground etc. so I think she may have had weakened bones due to being a twin.