Generally speaking, they are in the same "family" of laptop models, but they are not exactly the same laptops.
For example, the Inspiron 15 7000-7537 is a 2-in-1 laptop that has a dual core i5-6200u CPU and no dedicated GPU.
Always look at the specs of the laptop since model numbers can become confusing. The Dell Inspiron 15 7559 has a quad core i5-6300HQ and nVidia GTX 960m. Some models have an i7-6700HQ CPU, others may have a 1TB HDD instead of up to a 512GB SSD.