Correct answer upstairs, I would like to add that the long strings between the first name (such as Albus) and the last name (such as Dumbledore) may also be named to commemorate some people. In fact, it can be based on personal preferences. There are various reasons, but usually they are not used.
It’s not surprising that two generations have the same name. Others add “小” to the name of Little Barty just to distinguish their seniority. If two people with the same name collide, they will add dotted names to distinguish them. This is also the case in China.
And not only the United Kingdom, but also many countries in Europe, America and even Central and West Asia have such a long list of full names.