I think the answer to this is probably yes! I booked to take my husband to Germany for his birthday a couple of months ago and it looks like the family member who was going to have our daughter might not be able to do it now. I called my in-laws to ask, if it came to it, would they be able to have her for the weekend. While my MIL didn't say no outright, it was pretty clear that she didn't want to.
To be absolutely fair to them, she hasn't stayed with them on her own before (she's 5) and they are in their late 60's in ok health. They see us on a regular basis and are generous grandparents in terms of presents, coming to shows etc. I do appreciate that as they've not had her on her own (she's pretty well behaved but can be a bit shy of the MIL) they may have concerns about entertaining her and how she would settle with them. On the flip side though, they had my stepdaughter to stay a lot when she was young and have had her to stay recently. Again -to be fair, she is now 19, had quite a lot to do with them when she was young and they were younger then too. But some bad part of my head is narked that they have always been so keen to have my stepdaughter but now won't have my daughter. Am I being mean and poor spirited?!