I just bought a older home and I turned one of the bedrooms into a TV area. I would like to take the back window out and make it a door to let the dogs out in the backyard. The house is brick and the basement is block. Right where I want to put the door we have a block window in the basement right below. It has a steel header above the window. My question is do I have to take out the basement window and fill it in with block or brick?

Nope. You're not changing the load significantly to need that. Good luck with your project!