An alternative to #2,1 from Nik is η δυστυχία αγαπάει παρέα. From translatum there is this:-
Studies show that the truth behind the old saying "Misery loves company" is more accurately "Misery loves miserable company".
Σκεφτηκα το εξης:
Μελέτες έδειξαν ότι η αλήθεια που κρύβεται πίσω από το ρητό «Οι δεινοπαθούντες αποζητούν παρέα» εκφράζεται ορθότερα ως «Οι δεινοπαθούντες αποζητούν την παρέα δεινοπαθούντων».
With all due respect, Theseus, since you've granted me the privilege to help you improve your fluency in modern Greek, that Η δυστυχία αγαπάει παρέα, in my eyes and ears at least, is missing an article. Let's clarify it by omitting the article in other examples with the verb αγαπώ:
Ο Γιάννης αγαπάει Μαρία / Ο Μήτσος αγαπάει καλοπέραση / Οι χαζοί αγαπάνε Τραμπ / Οι ναζί αγαπάνε Τραμπ.
In all these cases, I would definitely add the definite article before the verb object, and in the last two examples I'd rather omit the object altogether; even the subject in the last one, but that's another story. In other words, unlike love in English, the verb αγαπώ craves the article, can't do without it, at least in standard Greek. See all the examples in ΛΚΝ, for instance.
As for the versions with δεινοπαθούντες, in terms of register and style they bring to mind a see-saw; one side low, the other high, unbalanced because the use of that participle brings the Greek phrase at least a couple of levels higher than the English one, twice so the version with the double participle. And such imbalances make me dizzy; I don't love them at all.
Όμοιος ανομοίω αεί βελάζει.
I'd suggest Ο δύστυχος τον δύστυχο αγαπά, narrowing down to misery the general Όμοιος τον όμοιο αγαπά.
όμοιος τον όμοιο, για να δηλώσουμε ότι ο καθένας προτιμά να συναναστρέφεται τον όμοιό του. (απαρχ.) όμοιος ομοίω αεί πελάζει*. ΠAΡ όμοιος τον όμοιο και η κοπριά* στα λάχανα.
