Hello floraasi, thank you for your question. The windows are manufactured by Jeld-Wen. These are part of the Premium Vinyl collection. You can find the models here: http://www.jeld-wen.com/catalog/windows/premium/vinyl

The groups of three look like one large window to me. Hard to tell this far away!

They are often times 3 units that are mulled together (usually at the factory) and then installed as one unit.

Top Dormer - those windows look like 3 separate windows with framing/drywall between each. If you look closely I believe you will see between each window there is a very narrow area that is painted.
Bottom - those appear to be a "triple" unit. 3 individual windows are either attached at the factory, or on-site by the installer.