It's good but it's not totally great.
Really good to see a gritty Irish drama.
Given that Frank is played by the guy that plays Tommy Calcetti in The Wire it is hard not to think back to that series. Kin is not trying to be The Wire but it does have many of the same undertones. It just seems to lack the intensity. There feels to me to be a disproportionate amount of time given to the family dynamic when the characters themselves are established quite early on and don't seem to grow much throughout. None of them have much charisma either, so there are no really interesting dynamics between them. It's just that they are all a bit angry but calculating, and some are angrier than others and some are more calculating than others.
Michael, an estranged father, much calmer but still as calculating and also a complete monster (ie. the only character with any obvious form of potential for internal conflict) is the only interesting character apart from some kid who carries out hits for the opposing group, but that character is largely left alone (possibly saved for later). It would make sense more if the series as a whole was focused on Michael or if the other characters were less one-dimensional but it darts around, feeling a bit uncertain about where it wants to go.
Still very worth a watch but it feels a bit drawn out to me because ultimately it lacks focus and/or character development.
There will obviously be another series, so my hope is this is just a taster of things to come. I am not sure the writers have the panache to elevate this series from something that is pretty good, in to the realms of excellence.