Err, I really think of this as a business and money issue; and family doesn't mix well with business. One day, mom and her husband will pass, hopefully a long ways from now, but it will happen. I have two sisters, and a brother; as well as her husband has a daughter and son; so that's splitting everything 6 ways. Noone knows exactly what their assets are, but as in many cases, it's primarily the home/land. I know they have floated the idea od basically forcing the home and property to stay in some kinda trust, that acts a lot like a Timeshare; in their mind, it all stays together, and everyone can use it... The issue is, we are spread between 5 states, and only me and 1 sister live close by. That particular sister really likes the idea of a timeshare kinda deal; until you start sending out property tax, maintenance, power bill and repair bills; and 4 out of 6 live over a 1000 miles away. I live the closest, and me and wife have briefly discussed; and I know what everyone is thinking. They Assume Paul will mow the yard, keep up with the house, ect, and all is good. Sorry, not doing that. Also, you live 1000 miles away, how are you gonna feel when you get the $2500/year bill for taxes, power, insurance, mowing, ect.
Every family has its own dynamic; But I feel I have an obligation to My family (my wife, my kids), and part of that obligation is to not put myself in bad financial situations over some random extended family (siblings, and 2 step siblings I've met like 2 in my life). That's Not to say I would be blood thirsty or greedy, but im not gonna pay $2500/year to keep some kinda extended family peace, I'd much rather use my money to set my own family up. That's not even taking into account step siblings, or random people you don't consider family; no I'll will to them, but no good will either.
So, I get the OPs siblings situation, it might seem greedy, but they owe our OP nothing, and their families everything, and if that means you don't see the aunts/uncles at holidays, so be it.
For our OP, I really think you need to do a deep think in what the property is worth to You, and don't over extend yourself. If $900k is what it's worth, don't pay more; if 1.2m makes sense, you it works for you, do it. This isn't Really about feelings, it's about Math.