i dont think they need a realtor to chime in about this, unless Consolation WANTS to negotiate, which would be a big mistake , imho.
they will gain nothing by saying yes to these selfish neighbors.
just say no.
Interestingly, the email from their lawyer was to our lawyer. She chose to pass it on to us. I think there was a kind of implied “No Comment!!” from her. 
I have a couple of friends who are local realtors. Tomorrow I’m going to ask their opinion on the value issue.
H says that if we say no they will come back and meet our terms. I told him that those are no longer my terms. I’m not doing this for $5K plus legal fees. Period.
They and their lawyer seem to have forgotten that we have literally no reason whatever to do this other than the goodness of our hearts. They just forfeited that.
BTW, we continue to have a fine relationship with the other neighbor to whom we granted the original ROW in order to enable him to sell the lot and settle his father’s estate. 
I think this is one of those situations where you want to offer as little information as possible. They will likely try to use anything you tell them as some sort of hook to convince you to do what they want.
So just say a simple no - “upon further consideration we have decided to not allow this property division” - and leave it at that.
If you mention devalued property, extra cars, construction noise, the 5K that you wanted, their nasty lawyer, etc., they may come back with a different realtor’s evaluation, offers to abate noise, extra money, a new lawyer, etc. You can save those arguments for later, in case you need them, but don’t crack open any doors that they can try to wedge a foot into.
By all means talk with a realtor, but you don’t need to share what they say. Not yet, anyway.
I agree to what greenwitch has advised.
Is your H willing to “just say no”?
One additional house creates more traffic than just the residents who live there. There will be additional delivery vehicles, contractors and subs, installers, maintenance services, friends and family visiting, barking dogs, parties/celebrations, more noise, dirt and dust— all ongoing. Is there ANY possibility that the neighbor could somehow subdivide anyway, WITHOUT getting your approval by going directly to the city/county?
I would also say no. For me, the “unknowns” would not be worth $5,000 towards a new bath. At the very least, saying no at present could only improve your final negotiated compensation.
Just say no in the vein @greenwitch suggests.
If there would be only one in-bound drive for those houses check your local zoning. Where I live you can put a driveway in for one split but if a second house goes in on another split with plans to use the same driveway the drive has to be upgraded to road standards so not only wider but far more expensive.
I’ve read that if I’m represented in a legal matter by a lawyer, the other party’s lawyer is supposed to communicate with my lawyer, not me.
As someone who recently endured a building project next door – at a very very leisurely pace – don’t underestimate the inconvenience of new construction either. Noise, lights, equipment, mud on roads (and hence on your tires and in your garage ), dust in air, etc. It’s fair to be compensated for this as well. (And now that it’s done, it’s lit up like a Christmas tree every night, so we see it round the clock, so our view is irreparably altered.)
If you are not legally compelled to do anything now, you have the upper hand. So yes, you can demand both civility and monetary compensation.
Good point about the construction disruption. We share an extended drive/road with 2 other homes, one of which was built a couple of years ago. The construction took a year and during that year my driveway exit/entrance was blocked by construction related vehicles about 75% of the time. It’s super fun to find you can’t get out your driveway to get to work, pick your kid up at the bus stop or get to an appointment because it’s blocked by one or more trucks. The fun continues when you traipse around a construction site trying to find the owner of the truck so you can ask him to move, only to have him give you attitude about how you’re interrupting his important work and maybe you should just wait a half hour until he’s done and can get to it. About 10% will apologize and go move their vehicle, 50% will roll their eyes and act like you’re inconveniencing them before they slowly go move and the remaining 40% will actively argue, call you names and yell that you need to just wait until they get around to it. Fun!
Agree with all the others that $5k or even $10k is not nearly enough compensation for the disruption, additional traffic, loss of property value and risk of potential future expense. My friend who is a consummate diplomat taught me a phrase that is perfect for situations like this. You want to politely but firmly refuse and avoid giving reasons or objections that will be viewed as things for them to pick at, argue with or try to solve. Here’s the magic phrase, “Thank you. I’d prefer not to.”
Repeat as needed.
How do you really feel about the whole plan of another house being built there? How much will it impact your home? If it is going to have a negative impact and you really don’t like the idea then I’m in the just say no crowd. You were trying to be nice to do them a favor. Their lawyer’s attitude kind of gives you a good “out”.
CF is absolutely correct about represented parties. The other lawyer can get disciplined by the Bar if he talks to you bypassing your lawyer.
And momof3 is correct that with an additional house there could be a requirement not only for a wider road but also for additional fire safety features like an extra hydrant, fire truck turnaround, etc. and drainage mitigation. And then you will need to create a new road maintenance agreement…
I am also just say NO team!
And any easement goes with the deed of the property on which it lies.
I like the phrase above “Thank you I prefer not.”
and also, “The original kindly granted easement can stand unchanged.”
Don’t let them run up YOUR attorney bills. Have your attorney say NO, and we will not discuss this further. Tell your attorney that (you don’t want to discuss it further unless there is something legally compelling you AND you do not intend to let them run up your bill.)
Talking to realtors is OK. You might also find out a bit of information for free by talking to your town/county planning department. What are the legal requirements for subdivision? If access is not there, then they have a non-starter. And the planning department will tell you stuff for free (other than your time). Do it via phone not email, since those records can be requested for public view.
^ ^ this “Don’t let them run up YOUR attorney bills. Have your attorney say NO, and we will not discuss this further. Tell your attorney that (you don’t want to discuss it further unless there is something legally compelling you AND you do not intend to let them run up your bill.)”
Notice the NO votes seem to be nearly or all of the comments. Definitely end your attorney costs with the end of discussion as above. Their problem, not yours. You owe them nothing. Relax and forget about it. Keep it simple, it is their issue to figure out, you lead your lives as you have. No need for you to look for solutions or accommodate them.
I agree with you, @Consolation. Given their response and lack of appreciation for your first previous generous response to their original request years ago, just say your offer is withdrawn and you are declining their request. Done.
You obviously bought your land out there because you wanted peace and quiet. Remember the neighbors form h*ll thread a few years back? What if that happened with residents of the second house they build? You would be taking all of the risk with none of the benefit. Nothing to gain- everything to lose. This is a huge NO to me.
I am the world’s most accommodating person and I would say No with zero further discussion. The end result would make your house harder to sell. They can move. We down sized to 2,650 sf and frankly another step down would not be worth the moving expenses so I question their motive.
They can subdivide, but they need to be able to access the new lot. There are two possibilities: we agree to change the easement, or they access it from the end of a private road nearby.
To date, the latter option has been impossible. In 2010, when our good neighbor originally subdivided his 25+ acre property to create the lot, he tried to get that access, which would have been short and much cheaper, because the lot was literally at the end of the private road. The developer of the rest of the land on the private road had retained the right to hook into the road and would not give it up. He wanted good neighbor to sell him land so that he could put up more houses. I gather that in the meantime the ownership of the road has in some fashion been transferred to the owners of the other lots, and all of their permission would be required. The wife of the couple told me that although those people were all willing to let them have that access, it would require all of them to alter their mortgage agreements.
I know this is complex. 
Anyway, as far as I’m concerned that is now their only solution. They can offer to pay the costs of those other property owners, which will likely include an appraisal for each one, at least $538 in filing fees and so forth for each one (as we discovered 8 years ago), and legal costs for each one. I think there are probably about 7 houses. And who knows whether actual refinancing will be involved…and the road agreement.
I bet it runs them a lot more than we were asking for! I am willing to eat our current legal costs to be done with it…unless a much larger amount of cash suddenly materializes. Which it won’t.
I will be drafting a new email to send to our lawyer, instructing her to tell them we now have no interest in granting the amendment, and to please convey that and suspend any activity on the matter.
Their motive is to make some money LOL. I see it all time time around me. People buy 10 acres, build on a corner of it and then split and try to sell off the rest (to pay for the house they built).