My parents.
PILs effectively live for their children, basically sacrificing anything of their own (save a couple of unintrusive interests, and a shrinking group of friends). They help with our children after school on pretty much a daily basis, and we see them most weekends at least once. If they don't come on holiday with us, they don't go on holiday.
My parents are very independent people, who have a very active social life, several holidays a year etc. They raised my sister and me to be the same. That said, if we ever need anything, they are generally there.
Though there's only about 10 years age difference between them, DPs and PILs are basically from a different generation to each other.
DW really struggles with the difference in approach, and has a tendency to interpret it as my DPs not caring.
She takes it so personally that she basically won't see them anymore.
I don't see them as often as I'd like, in order that we don't constantly argue about it. It feels like this will reach a head at some point.