How did we go from friendship and romance between races to offspring viability? Nothing says a pair has to be capable of bearing viable offspring to have a relationship, even a strictly physical one. I think the biggest thing would be overcoming cultural differences and finding attraction to one another. As for breeding... well, things don't have to be a tab-A-into-slot-B type thing, but I'm sure you all have imaginations... and that act wouldn't have to produce offspring to be considered. The real question is this: Are the horse and squid into that kind of thing?