I've had this plant a while now, the parent plant (stem in picture) died and I have been trying to get the little fellow in the picture to grow. He is attached to the roots of the mother plant so I cant repot him.
Noticed a couple of weeks ago that he was starting to look a little sick. I have been trying not to overwater, so only watering when the soil in the bottom of the pot is dry. Its located in a downstairs bathroom, getting lots of light in the afternoon, but recently is leaves have started to split and curl, and it has some strange marks on the leaves. Is there anything that I can do to help this little guy?

Can you post some pics of the entire plant?
The light spots look like scratches. Any pets have access to it?
About how often do you water? I know you said 'when the soil at the bottom is dry', but about how often is that? When you water, does water come out the bottom? Have you fed it at all? Depending on the light it may be able to handle a dose.

I think it's Ti plant (Cordyline fruticosa.) If so, it would do better if the soil is kept consistently moist. How are you determining that the soil at the bottom is dry?

This would be easy to repot, just pull the whole thing out, chop off the dead stem, and if you find a root pie at the bottom, chop that off, knock off the rest of the soil, and it will probably fit back in the same pot, with new soil. The surface of the soil when you are finished should be at the same level, with the plant not any deeper or sticking out farther than it is now.

I hid it away to keep my cat away from it, so I don't think its her. I keep that room shut to keep her way from it. I have a feeling that it might be because we had a heatwave recently in the UK, and he was in a window that gets a lot of afternoon sun, so I don't know if that was the cause of the spotting? I really don't know what type of plant it is, I brought it many many years ago and it grew from a "normal houseplant size" of about 6 inches to about 5ft! I always thought it was a type of yucca to be honest. Then to my horror it died on me, (the stem you can see in the photo, is what's left of it, I've cut it off just above from what you can see on the picture) but it then sprouted babies! Then the babies died... I thought that this was due to overwatering at the time. What you can see in the image is the last one, and I'm very attached to the little guy and really want him to grow. I've been watering him sparingly. I've been sticking my finger in the drainage hole in the bottom and if its dry I would water. Not enough to run out the drainage holes though, like I say, I was worried about overwatering. I would mainly spray it until the top layer of soil was wet. I would day once every month/six weeks? I noticed a while ago that the new growth had stopped, but he didn't look anywhere near as sorry for himself as he does now. I've taken some new photos so you can see him closer up and in his home environment, its pretty rainy today though. Any further questions that can help fix the little guy please ask. Any help/advice would be really gratefully received.

When you water give it a thorough soaking and then let it dry out again. You're "teasing" it with the sprayer.

Agree. Do you have a pic of it when it when the tall part had leaves? It could be Yucca, I thought about that, but it just gives me more of a Cordyline vibe, as a first suggestion for comparison. It will do OK with less light than Yucca, and more likely to be encountered as a single-trunk houseplant.

Pics of the Yucca that is sold as a houseplant for additional comparison:
Spineless Yucca (Yucca gigantea)

Is the window in the last set of pics the only source of light?