1. He wanted to find out the answer to the question if the tweens have special bonds or similarities. To do this he traced sixteen pairs of tweens...(и перепишите это предложение до конца, а то в тексте видно плохо)
2. He found that many tweens had the same hobbies, phobias,many had suffered the same illnesses, and some had had the same type of accident.
3. They became famous because though they were adopted by different families, they both were named Jim, (а затем переписываем все предложения выделенные точками, начиная с Both grew...)
4. Scientists admit that our personalities maybe at least partly due to nature, on the other hand...( и до конца предложения)