I like the Scottish way of words: "natural", as opposed to "lawful". But then, marriage wasn't always the be all and end all of everything. Just look at Bastard William of Normandy.
The English word "bantling" (meaning "brat" or "small child") comes from the German word that means "bastard, child begotten on a bench" (and I'm not going to try typing it as I don't have the right keyboard), yet nobody would blink at "bantling".
From about 1830-ish, though, it is most definitely a pejorative, meant to demean and belittle.