Not much we can do without a pic or just more info. Trees sometimes grow in a leaning fashion, usually reaching for light, while other trees start out straight and begin to lean later because of some calamity. Two very different situations with two different answers.

+oM

If it's an Albizia julibrissin, I'd recommend pruning at ground level immediately followed by an appropriate dose of glyphosate. But, without a proper ID and a picture, it's anyone's guess as to what type of tree it is, whether there is actually a problem that needs to be addressed, what caused the problem, or what the best solution would be.

Here's a pic of the tree. I hope this helps.

It looks like a mesquite tree. It is not unusual for them to grow at weird angles or into multitrunk specimens.

the tree did not move the rock ... your dad did with the rope ...

enjoy it the way it is.. or get rid of it ... no other option ...

but before you get rid of it... think long and hard about why you guys are insisting on a straight tree... this one has much more character and uniqueness.. as compared to a plain old upright tree ...

most of us.. would pay EXTRA money for such a dramatic specimen..

and all you guys can think is.. well... i dont know what you are thinking ...

its really cool ... leave it alone ..

ken

ps: you could prune it up a bit.. and add some nice plants under it.. to make an incredible scape.. with a very dramatic tree .... as the centerpiece ...

A rock the size of the one in the picture (if that's the size of the one that was moved) could easily be moved by a tree that size, especially if the rock was adrift on pea gravel. The first thing I'd consider is whether the tree had grown naturally at that angle or if it had shifted into the lean. One could make an educated guess based on whether the pea gravel at the base of the tree had been disturbed. If the tree fell, after initially being more vertical, I'd suspect a poorly formed root system, most likely caused by roots being potbound at planting. In that case, there's not much practically that you can do at this point. You could just leave it as-is and enjoy it while it lasts or remove it entirely. If the base of the tree does not seemed to have shifted, I would definitely just learn to enjoy its character. If it grew naturally like that, it's roots are strong and there shouldn't be any long-term problem associated with the angle of the trunk. The bottom line though is that the two most reasonable solutions, in either case, are removal or love it as-is.

Thing is though we've seen pics of the tree from a few years ago (we did street view on Google Earth) and the tree was growing straight.

In regards to the rock, that is not the one that was tied to the tree. There is another one that is larger that is not in the pic. I am thinking we might keep the tree the way it is cause the kids (and the cat) like using the branches that are on the ground as a hiding spot. I'm not sure though.

Sounds like it was planted incorrectly then. Unfortunately it's a way too common problem. It's hard to tell what the tree's future will bring.