Hey there CM - I've been thru some crazy shit with regard to elderly family and neighbors wanting your family property.
Here's the deal the way I see it. Humans by nature are/greedy bastards. I'm sorry IF I upset anyone. Not every human but when it comes down to the all mighty dollar and land is worth a lot of dollars, you sir can count on greed (a manifestation of hate), to be a motivating power in this type of human behavior.
Your neighbors and even family, some of them when they see "perceived" weaknesses the greedy folks with try and take advantage. They see you and your siblings not in 100% agreement or even getting along. They see your father much weaker physically now than he has been for all your life and his. He is now seen by the greedy bastard neighbors as a person they can try and take advantage of and probably so do some of your family.
You are there helping him, you are seen by the greedy bastards as a nuisance, in the way trying to hold on to the hear and now and keep your father here too. They will try and take advantage of your situation by working on YOUR weaknesses as well as your fathers weaknesses.
This is all motivated by hate. Your best defense and I mean this from experience is look to your love for your father and the love in your world as guidance and motive for you. Don't get caught up in all the negative DRAMA ... they will try and suck you into, then YOU make a mistake the greedy bastards will be there at the time of the mistake and take advantage to try and grab a hold of whatever it is they want (usually money and or land) at your expense.
So you gotta first and foremost take care of Dad with love and respect. Try and find one of your siblings that you can get to help that is not motivated by greed. Safety in numbers.... herd up and line up like the buffalo and face down your fear, your greedy bastard neighbors and relatives. Show strength with caring and love and be firm and whats fair is the path; love wins every time over evil and hatred.
Be glad you're not one of them, and try and get a friend to help watch you and your dad's backs.
I'd probably (and do) have a few dogs... the greedy bastards can build a gate, come thru the gate and your dogs got your back. That way its not YOU in their faces, just a handful of teeth. Dogs have a knack for spotting evil too so they will let you know whom to trust and not to trust. You may be be surprised about whom they see as a threat.
I guess my point is this: your perceived weakness by greedy people is a sort of open door to them getting into your life. Sure up that perception by showing strength & love.
My mom used to always say to me when I was pissed off and wanted to kick some ass, she would tell me to; "kill em with kindness".
Showing anger is showing your weakness.
Cheers and good luck.. probably giving them buds isn't a great idea !! (although it would likely be the best cure). We are as a society are not there YET.
Figure out the motives of the few, that will help guide you thru.
Peace and respect
I wish I was your neighbor, WEED have a lot of fun, no drama.
Sorry I got all wordy.. I was trimming earlier... a sort of fog is setting in now... I think I'll go and.......puff.