To think parents in law have a favourite grandchild

[Cyclingwidow15]

They have my nephew all the time! Happily have him for full weekends at the caravan because SIL is working one day at the weekend, so she gets fri and sat to herself. If we ask them to have our 2 for just one night it’s always begrudgingly agreed or sometimes they say no and give an absurd reason why. We rarely ask because of this response. They have never taken them to the caravan for the weekend. Luckily my mum is amazing and helps us out a lot.
AIBU to think this is favouritism? It’s starting to make me really cross

What age are all the kids? It could be that yours are more difficult ages, or the fact that there are 2.

Or it could be favoritism! It does actually happen.

You can't change them ...... what does you really DH say?

Is SIL on her own?
Does the childs paternal GPs take an interest?

Nephew is 3. My two are 4 & 6. SIL has a husband and his parents also take my nephew to their caravan regularly for weekends away. They probably have him even more often than my in laws do tbh.
My husband says he’s given up caring and it’s his parents who are missing out they are never going to change! He’s right I know but it’s still really annoying.
They have another grandchild as well and not much involvement with that one either really.