@Angdronell Durant Finishing probate is the preferred way to handle the property of owner(s) who have died. However, you can do many things with a property without completing probate. You can get (buy) a quit claim deed from the three descendants who you are in contact with and then just start using the property as your own. Rent it out. You can even resell it, though you should make clear that you're only selling your interest, which you expect to be 3/5ths of the estate.
If you rent the property, after 10 years you can file a Quiet Title action and obtain clear title. Or you could proceed immediately to probate the property and assume you can notify the remaining heirs by publication (requires the Court's consent). The property doesn't have to be probated. You just won't have clear title now. Clear title is likely to be needed if you want to sell it for top dollar or you plan to get a loan against the property.
Hm. I would do some research on the estate laws in Texas, just so you know what you are dealing with. Is there a known will leaving everything to be divided among the 3 (which is good) or was nothing ever put on paper(bad)?
Purchasing the "shares" of the property does have it's downside if someone later produces a legitimate will that leaves the house to someone other than the 3 siblings, but if you are getting control of the property for a steep enough discount it could be worth the risk.
It seems to me that in this day and age tracking down the 2 missing siblings shouldn't be THAT hard. The 3 siblings know the missing siblings legal names, and SHOULD know birthdates and old addresses. Maybe get legal contract from the 3 sibings agreeing to sell their shares for $XX within a certain time frame, then use an heir locating service to at least show a good faith attempt to find the other 2.
BTW, it is quite possible that these 3 know more than they are telling you. Inexplicably, people have been known to lie when $$$ are on the line. Shocking!
You can hire a PI to go beyond "skip trace" and get to "where do they lay their head at night". Be willing to spend $$. OR..
You can buy the shares you can get (outside of title), then carry one in probate court with a partition and sale suit. OR...
Heirs can add a partition and sale suit inside the probate case. OR...
Have administrator appointed for the sale, get court permission, and request the missing heirs' shares from the sale be put in the registry of the court.