FAMILY, they can be a blessing, but they can be also a pain in the b...!!!

I hope your m-i-l has learned from this at least...no one has to tell you how to live happily and this was the very wrong way, because it has offended you and risked the life of the kittens...

I hope very much that you'll be able to retrieve the kittens...and that your p-i-l will be more attentive to things like this the next time...

Good luck!!!