There is a bonebed of several T. rex specimens ranging from younger specimens to older ones, this would suggest that T. rex did take care of its young. It’s still not very solid evidence though.
What we need is fossilized footprints of dinosaurs of different ages walking together.
There is fossil evidence to suggest that sauropods moved in herdes with full grown adults up front and younger ones in the back. They don’t take care of their young though, most of them were so large they would probably crush their own young without knowing it. That’s why they just lay hundreds of eggs with the hopes that at least one of those individuals will reach adulthood.
I guess that theropod dinosaurs like T. rex had instincts to protect their young for some time. The oldest T. rex that paleontologist have ever found was only 28 years old. Unlike what Hollywood movies like Jurassic Park make us believe, T. rex had a very dangerous and harsh life.