https://www.reddit.com/r/Infographics/comments/qps9gy/indoeuropean_for_two/

Check out this infographic for a more visceral sense of the family. The word for 'two' is similar across most of the indo-european family. Obviously not all words are like this, but it's an interesting graphic.

Another example of how a family is related but not mutually intelligible is that the English "black" and the French "blanc" ('white') come from the same origin - an older word referring to stuff left over after a fire. The English branch took this to mean charcoal, and the French branch took this to mean ash.