For some Rank X and S u no longer need 2 Monsters but 4. All of them need to be in the Grand Parent Generation.
But there are also some where u just need 2 like before.

https://game8.co/games/DQM-Dark-Prince/archives/436089

Estark here is a good example.

yeah, how anyone would figure the 4 mon combinations without without a guide is beyond me. . .

ok thanks that website is gonna be really helpful. I heard that the Lord of the Dragovians is an easy x rank, I think ill go for that one

that one is one of the few i discovered on my own, because it basically uses all the ones i was combining anyway.

i mean, many of them to have logic to them, like the boss of a main series game, requires all the other bosses from that same main series game. but then some, reauire 4 endbosses from the other series games to make the next one.

it was interesting how they all kinda funneled into the last 2 X types. like, i made a bunch of S ranks that required specific A's and then those S's combined into an X, then i made another X from other S and A, and then combined those X to make the next X, and then there were 2 other X that required other S, which then combined to make another X, which then imcombined those ones.

but yeah, the ones that need 4 specific grandparents are especially hard.
like buntzenburner(a B rank. . ). the logic for that one makes sense working backwards, knowing what went into it, but it's something I never would have discovered on my own

making Zoma and Estark, the last X mons i made before 100% the encyclopedia, pretty much required making all the other ones first and combining them in a specific way

Well, for this game u could actualy figure out even X Rank on your own if u rementer to look into the Systhesis preview.
U just need to show "not owned" Monsters and "any" as material.
The ones at the beginning are allways those u had the material in the past. Just repeat that every time u got new Monsters.
The hard part is finding all the Monsters that are exclusive from Eggs. Finding all of those can take a few days.

the 4 grandparent combos don't work like that. reverse synthesis won't show you, unless your monsters have the correct grandparents

example : Balhib
firn fiend + magmalice + stone golem + coralossus
if you have all 4 of these in your paddock, it will not show you the balhib.
you have to combine the firn fiend and magmalice together to create another firn fiend or magmalice with both of those as the parents.
then combine stone golem with coralossus to create another firn stone golem or a coralossus that has those as parents.

only then would it show you the balhib can be made.
if you were just combining monsters randomly or whatever, you might not ever stumble upon this combo