Well,ladies and genltemen.So I think it's time to practice in english a bit...
What can i say about roman languages...i think the reason of their similary is very simple..just recall the influence of the roman empire.the latin language was just a bit changed by local people and they gave own dialects.later those dialects of latin became independent languags(if i can say so).
Next:there are a lot of latin words in any language because europe used latin as the language of knowlage,the language of culture and so on.evrybody used the latin languge as the way to seem well educated.there also a lt of latin languages in russian,but it also has some greek,german and french words in the lexicon(or,i forgot about newly popular english...)