To be fair #18 isn't an Android in the traditional sense.

Well, the original Japanese word is Jinzoningen, which can be accurately translated as "Android" (the literal translation of Jinzoningen is Artificial Human, which is exactly what an Android normally is)

However #17 and #18 aren't robots like #16. They're more like Cyborgs. Humans who have been upgraded with mechanical parts. That's how Cell was able to absorb them. They're still mostly organic.

This is different than how the others we see were built. For example #8 was made from dead bodies reanimated with cybernetics and #20 was a robotic body with a human brain.

i already know that 18 was a human once krillin mentioned that when everyone was WTF'd when he showed them his kid

I havn't seen it, but from what I hear Krillen dies often

Krillin is kill?