The Grand Tribunal and the Hiberian invasion

In the summer of 1195 the Grand tribunal convenes in Deurenmar. The Rhine Tribunal issues charges against the covenant of Luctatio and 4 tytalus magi therein for having commissioned a plague to stop Fredrick Barbarossa in 1174 in his campaign in Northern Italy, thereby interfering with mundanes in a potentially ruinous manner. All 4 are marched.
The Transylvanian tribunal brings a petition to require the Theban to allow bonisagus magi, regardless of tribunal affiliation, to claim established apprentices from within the tribunal. They are joined in an alliance by magi from the Stonehenge tribunal who similarly want to force the Hibernian tribunal to press hedge magi to 'join or die'. the first measure is narrowly defeated, the second more broadly so. Durring the discussions it is revealed what the relative ease if for Magi to immigrate to Hibernia and set up new covenants, and the member proposing the rule offers an invitation to any magus needing a new covenant to "just move to Hibernia and set up your own, and we will take this lost tribunal back from within" While the vote was lost it is apparent that many magi seem prepared to heed that advice...

Does Prometheus know any Tytalus from Luctatio?

I'm going to say, given the description of Kronos, that it was his home covenant, so yes, Prometheus will have known all 4 Tytalus magi.
Of course by the time the ruling is handed down, none of the 4 are to be found at the Grand Tribunal, and you wouldn't bet on finding any of them at Luctatio either.
The other 2 members of Luctatio are a 5th Tytalus and a Jerbiton found innocent (or at least lacking evidence against them) by the Tribunal.

Oh, my parens is marched...? Or did he leave Luctatio before these events? Can this be settled without the marched magi being executed? Does it have any consequences for me? Is Okeania at the grand tribunal as well?

Okeana is at the grand tribunal as well. marched magi might be able to escape, but it only rumored to actually happen, and even then they continue to be hunted. There are no direct consequences to you- having a parens marched for mundane interference doesn't even cause rumors about your reputation...

Do I have a reason to care for Kronos? The way I've written my backstory, I had a relatively mild apprenticeship - compared to the standards in our house. If that is the case, it's likely the same for Okeania?

Hugh listens to the speech, and pays attention to who seems particularly interested during the speech and any groups that form afterward, who seem to be talking about Hibernia and/or planning to settle. (Just mundane wandering around the crowd hearing conversations.) He just wants to get an idea about who else might be planning to head there.

Whether you care for Kronos is up to you- Okeana will likely do the opposite just to challenge you.

Magi headed to Hibernia seem to be getting together in groups to discuss what covenant they will form there, typically groups of 5 or six, though these shift over the course of the tribunal as interest waxes and wanes for various individuals. a general consensus is to meet in Wicklow and set out from there...

In that case he'll propose to her to provide our knowledge about Kronos habits and thinking to help catching the criminals. Prometheus does care about him and does think about how this could be resolved without concluding the march and this way his sister and rival might do so as well. [Should it roll guile or intrigue or both?]

Does taking part in the grand tribunal take the better part of summer?

Between travel and the tribunal itself it takes roughly a month. Continuing to Hibernia can result in a late summer adventure...

Okeana will roll her eyes "Of course you would betray our parens, should have seen it coming since you refused to do in those street rats in Syracuse. Be on your way then, I'll have nothing to do with it." (I'm going to move the hunt to a different thread)

Ok, so if the hunt, or Prometheus part in it, resolves really quick I might do something else but most likely summer is lost for seasonal activities. Correct?

After learning where people are generally meeting in Hibernia, Hugh will try to find the member who suggested that people settle, with the intent of finding out if maps are available.

The summer season you can have 2 months. The hunt is in the fall...

The magus did not bring any maps, but assures you they can be purchased in London.

Hugh will see if the library or the redcaps in Durenmar have any maps available, or if there is a redcap outpost on the way down the Rhine that might.

He will also look for any groups that include people he knows, if he can't find such he will arrange travel based on whether he can find maps in Durenmar or not, stopping in London to get one only if he needs to.

You are able to acquire a map, though not a great one, of the coast of Ireland for that region.

That will be enough for him, and he will head directly for Wicklow.

meanwhile word has spread through the tribunal of the pending 'invasion' and numerous young magi out on macgnímartha decide to head to Wicklow...

Arnar is among those who decide to check it out, taking form as the white-tailed eagle he will have a good view of the invading forces. Before he goes, however, he talks to his sept-mate, Sionnach, to ask whether he too will be heading that direction.

Do he/they have anywhere near Wicklow, where they can keep human belongings. like a change of clothes?

You could always set up a camp somewhere nearby, or rent a room. In terms of covenants Lambaird is the closest... and dedicated to preserving Irish traditions.