Oh yes, bettas can hybridize!
ALL bettas belong to the same family... in fact, they belong to the same Genus -- Betta.
Bettas come in two breeding styles, mouthbrooder and bubblenester, and there are several groups within these two divisions:
Bubblenester -- Splendens, Bellica, and Coccina groups
Mouthbrooders -- Picta, Pugnax, Waseri, Akarensis, Foerschi, Albimarginata, and Patoti groups
Any bettas within the same group can hybridize with one-another, meaning splendens can easily crossbreed with imbellis, smaragdina, and rubra, for instance. Outside of that, hybridization can occur, but it's more iffy. You'd have more luck breeding moutbrooder to mouthbrooder and bubblenester to bubblenester, but I don't doubt it is probably possible in some cases to breed mouthbrooders to bubblenesters and vice versa. The less closely related the species, however, the harder it'd be to get viable hybrid offspring.