I'm going to repurpose baby clothes into dog clothes instead of giving them to my sister in law
Do you feel weird about doing that to your sister in law?
I do feel bad that I'm giving baby clothes to my dog when it's suitable for humans
It is good to take good care of your pets but a human child would have more need of those clothes. It will hurt your sister in law deeply that you don't care about your nephew or niece.
I am a dog person and I love my dog just as much as I love any child. I have a right to decide what to do with the clothes.
It is expected that you give these clothes to someone that can use them for a good purpose.