Consensual love between those of consenting age is always beautiful, regardless of breed, race, sex, tribe, or whether both lovers are Garou.Tribebook 3 - Children of Gaia, p37
We breed where and when we can. [...] And believe it or not, occasionally we fall in love with other Garou. Anathema though it may be, I'm sure you know difficult it is to deny your feelings.Tribebook 9 - Silent Striders, p34
Wow, the litany has nothing to explicitly ban happenings (no wonder, taken how individualistic they are), but has one debatable position here: "Honor yourself", which can also mean "avoid the inbreeding sickness"Breedbook 1 - Bastet p37, but that sounds more like a weak "Better don't make Metis" than the treasure trove of information the Garou hid under their first litany item.
That's why I think it's more an urge to breed than anurge for sex. A shark wouldn't understand the differenceanyway, and it took me some time to get used to the ideaof mating for mating's sake.Breedbook 8 - Rokea p42