Welcome to the forum.
You don't mention what brand of cameras you're using, but it sounds like Canon. It also sounds like you're shooting with a 'crop frame' (APS-C) sized sensor. In which case, a truly wide angle will come from something like the Canon EF-S 10-22mm F3.5-4.5. I used that lens for several years, shooting landscapes, weddings etc. Just don't use it too much...as it often makes you want to get really close to your subjects, and that causes a lot of perspective distortion. It's easy to forget that while shooting.
There are other options in that range, the Sigma 10-20mm has a good reputation.
The 18-55mm range is considered the 'normal' range, on APS-C cameras. The common 18-55mm F3.5-5.6 is usually called the 'kit lens' as it is bundled with most of the entry level DSLR cameras. Not really what most would consider professional level equipment for a wedding photographer.
If all you have is a 70-200mm....then you should probably get something in this range, before you get an ultra wide angle lens.
One of the best options is the EF-S 17-55mm F2.8 IS. Large maximum aperture & top level image quality...although, quite expensive.
Another option, (the one that I used for years) is the Tamron 17-50mm F2.8. Pretty good image and build quality, not nearly as expensive as the Canon 17-55mm.
Another option would be the EF 16-35mm F2.8 L or the 17-40mm F4 L. Both are high quality lenses, but the main benefit is that they are EF and not EF-S lenses. This may not matter to you now, but if you ever decide to upgrade your camera to something with a 'full frame' sized sensor...then you won't be able to use EF-S lenses (or similar lenses like the Tamron I mentioned). So something like the 16-35mm would be a 'normal' range zoom on a crop camera, but it would become an ultra wide angle on a full frame camera.