This is not as uncommon as you might think!! I see it fairly often in wooded properties around here, although usually one tree is considerably younger than its companion. I suspect the second tree is the result of birds (or other tree perching critters) 'planting' it but it could be a natural occurrence as well.

Most often they are left alone. They seem to manage quite well in these situations so unless it is in a highly cultivated or landscaped garden, I'd be inclined to leave this pair as well. For sure the second, skinnier tree is far too large to dig out and doing so would impair both root systems.

Big tree looks like pine but what is the smaller one?

Some kind of broad-leaf tree.

Totally agree with G.G. It’s just nature and I’ve seen it often. There’s a couple of Scots pines down the road from me with an Acer right in the middle. Unless they're going to fall on something important I’d leave them alone.

I've seen a red maple growing out of the crotch of another, larger tree. So even closer than the above.

And furthermore, the smaller tree should be moved about a foot or two to the right so it'll be at least another 50 years or so until it has to be moved again. Also, use a small, small shovel when digging so as to damage as few of its fibrous roots as possible.

(Disclaimer: I am not being serious.)

What's odd is that the smaller broadleaf tree didn't grow/lean outward away from the pine in search of more sunlight, an opening in the canopy. If these were both pine trees, this wouldn't be surprising to see.

Seems like it’s usually young hardwoods growing up against an older pine. I guess pines just don’t have the ability to shade out the competition. Black cherry is bad about doing this, but as someone already mentioned, it’s likely the birds sitting on the branches and pooping out the seeds.

Some kinds of trees located inside of stands are often able to grow fast enough despite significant shading to make a serious attempt at getting up into the full sunlight directly overhead. The aforementioned maple for instance, if it is one of the large-growing species.

There are many species of trees that are not dispersed by having fruits attractive to birds in combination with indigestible seeds. And yet are still able to seed around.

As GardenGal says, "not as uncommon as you might think!! Here's a pair in my woods. Douglas Fir and a Western Hemlock on the left.

I've seen some beech that actually merge above ground...