My names book has Seaton/Seton as French, meaning "from Say's Farm" - which I admit sounds like "we've made up this meaning 'cos we couldn't find a real one"!
Kilby sounds & looks like a variation of Kelby. This is listed everywhere as Old Norse, and the predominant online meaning is "from the farm by the springs". My name book says "ridge farm". I'm pretty sure that 'by' indicates a farm or settlement, but I don't know about kel/kil.