The KIT vowel, /ɪ/, which we find in the word sit, and the FLEECE vowel, /i/, which we find in seat have different pronunciations in Southern Standard British English and General American. In Gen Am they are said with the jaw slightly more open than in British English. So a Gen Am /ɪ/ may sound more /e/-like to someone used to British English.
In the Western United states, the KIT vowel changes when it occurs before velar consonants /k, g/ or /ŋ/. We say that this new sound is an allophone of the KIT vowel for these speakers. When people who speak this variety of English have a KIT vowel before a velar consonant it becomes much more like a FLEECE vowel. It is longer and more close.
Because of this when these speakers say, for example the word sing, it will sound a lot like the word seeing to somebody who does not have the same accent. These speakers also have a different vowel in words like bag. Here again we have a velar consonant, /g/. These speakers will use a vowel that sounds like /eɪ/ to other listeners. For people listening, the word bag may seem to rhyme with the word plague.
These different possibilities for the vowels which occur in words like king and kin could be why the Original Poster finds these types of word confusing.
This article here talks about Western US vowels before velar consonants