what do you mean, "the kittens will be wild in no time"?
Get the "owners" address and when the babies are age 6 weeks (assuming they are outdoors) go steal them! Have stolen plenty of babies and moms with jan from bad owners- just be careful not to get caught. If the shelter ( 2 or 3 weeks later when you say you have babies up for adoption and possibly a mother) asks where they came from, "someone dropped them on my doorstep" if they say it looks like the ones that came from... say back to them, "Yeah, I thought so too! Funny coincidence huh?"