Underneath the world map you will see a number of tick boxes adjacent to the patents. Each tick box relates the priority date that the patent we are looking at is related to. The priority data section will give you that patent's priority number and date. In case of multiple priority numbers, you can scroll horizontally on the page.
An additional tick represents a divisional or continuation update to the patent and refers to what priority date this update is referring to. This is true for every other tick going forward.
If each patent has a matching tick in its box, then it is part of the same family as it is referring to the same priority date and is thus protecting the same invention. These are what we call simple families, if more than one patent has three ticks in the same box then again it is still part of the simple family.
However, if there is a gap in between two tick boxes then this patent was not filed as a continuation or divisional update to that specific priority date with a blank. This patent is no longer part of the simple family and is part of the INPADOC or extended family. This is because the patent has the same common scope but lacks the exact same common priorities.