Don't have much advice but how about getting everyone for a potluck dinner. Everyone brings something and maybe the stress might be reduced some. Just a thought.

Maybe you could just sit down with them and ask them if they think they see their grandson enough. Or maybe ask them about their feelings about the whole situation without it getting into a heated argument. I do agree with Teri, maybe bring something small over to break the tension. Maybe if you already have other plans just don't tell the other set what you are doing. If that doesn't work, explain to them that right now your 11-year-old is being more mature than they are!!

I could see that the others would feel that your FIL gets to see your son more, because they live closer to you and it's easier to take him over there or for them to come to your house. Your FIL should realize that he is your son and has more than one set of grandparents, two sets that he doesn't get to see all that often. They should all stop keeping track of who has the grandson when and be happy he's part of they're lives. Many grandparents don't get to see they're grandkids at all.

There is another thing that they need to understand now. Your son is 11 and getting older and there will come a time when he won't want to go stay over night at Grandma and Grandpa's. There will be times you go to your parents and your son is at home because he wanted to go do something with his friends or has a date or something. What happens when he's an adult?

They should also be happy to see they're kids and not feel that your visits revolove around your son. Giving you the cold shoulder over it is really a childish way to handle it. My mother did that when DS was a baby. We'd go over there and they'd take DS and play with him and it was like we weren't even there! She then started to wonder why we didn't come over to visit that much and I told her why. They got better at having conversations with us and acting like we were there. She'd also take it personally if I ran up to get something and left DS at home with his father. It got very annoying.

I think you should have also stepped up and said something before now. You've let this go on for 11 years and most people would have been tired of it from the get go. They now think it's fine. They've been making you feel guilty and probably DS for allowing him time with all his grandparents. How unfair is that? No single pair of them are better than the others and he's the grandson to all of them.

Ignore them all, just as you would a jealous spat between siblings who think the other got a bigger piece of cake. Do what you know is right, please yourself and your immediate family (DH and son). Don't get invovled in their jealous feelings, it's their problem, not yours. I know that's easier said than done. I just think you need to learn to let it go, realize that you have done nothing to them. I think if you go out of your way to try to please anyone, it sends the message that they have a reason to be upset. Like you wouldn't be trying to fix it if you hadn't done something wrong in the first place. Since you didn't do anything wrong, don't try to fix anything.

Talk about the situation with your husband. Develop your own position as unified parents of the child in question (and as your own family unit). This is so that you and he are going to reinforce each other _even_ when there might be 'jealous feelings' or whatever on the part of the grand adults. They might naturally feel closer to you or to him and might then try to go to one or the other of you when they feel slighted or hurt. It's one thing to soothe them because hurt feelings hurt, but they shouldn't get to vent anger over your (either of your) partner's decisions to you.

People just have feelings. Everyone is an individual and their brains and moods are all wired together just a touch differently. They might feel jealous. If they have strong feelings they don't like or which they notice are not conducive to the kinds of human/family relations they want to enjoy and maintain then they should seek counseling on their own behalf so that they can improve their situation. There isn't really anything you can do about their painful feelings.
You can be as diplimatic as you like. Maybe they don't realize it, if they get to sounding like your child's presence is an object for which they all must compete. Gently asking if they mean to sound that way can give them a chance to explain what it is they are intending to sound like. On the phone you can enforce your own limits about any venting you will listen to before hanging up (they can be invited to call back when they can speak in a civil/communicative manner without venting). Just be prepared if you set a limit, to enforce it consistently and repeatedly (they will probably 'test' this new situation).

Issues between or within the grandparents are between or within them, and not you. Try to pull yourself out when/if they try to put you in the middle. An example of this which could be going on is a 'jealousy' of proximity. The grass always appears greener someplace else. All the grandparents undoubtedly love the grandchild and want what's best for that child and their family. If some grandparents live a lot closer, that's something grandparents who live further away might envy or feel jealous about. It can seem like the closer ones could or can always do anything and be close without even having to plan. That may or may not be reality, but when living further away and wishing to live and to be closer, it feels like something that could be going on... when stressed, maybe it feels like something that _must_ be going on. People who are depressed sometimes tend to thinking and feeling in this way. If any of the grands could be experiencing depression they need help and advice from their doctors.

identify what you know, in terms of the facts and try not to interpret (go through the sequences of events as they occurred and as they occur rather than ascribing 'jealously' because there could be a lot of other things going on); then identify how you feel about the different things; talk to the pairs of grandparents individually or together (individually allows you to personalize the same basic info, but together illustrates for everyone in a tangible way just how equal every one is)...

the most important thing though is for you and your partner to be solid and clear between yourselves as the parents (and family with your child)

All I can say is consider yourself and your child very lucky. My parents live 9 miles away and have not seen their grandchildren since Halloween. When I stopped to see them on Christmas Eve, they sent the kids' Christmas presents with me - so much for Christmas. Just tell the grandparents to "get in line" and smile as you say it. And thank them for loving you so much.