To me, giving unconditionally without expecting anything in return is indicative of true selflessness. If someone truly expects to get nothing back, any giving done is done with only the best intentions in mind.
This relates to an idea that I'm sort of conflicted on. If there are two people who are both doing nice things for each other and looking out for each other, the relationship is mutually beneficial. The reason it benefits them both is because they are both on the same page. If you have someone who treats another person as they would want to be treated, but that other person isn't on the same page, it may not benefit them.
If someone is "wired" to not form the usual emotional connection, the feelings and actions that are intrinsic to having an emotional connection with someone probably aren't going to happen. This would feel like unrequited love to the other person. On the flip side, the person without the emotional connection likely isn't going to be gratified by the actions or feelings of the other person. This could feel like a pointless relationship to them. I think most people would have trouble sustaining a relationship that feels like it takes more than it gives. Naturally, both people would want to do something to make the relationship meaningful to them. The disparity in what these two people need to have a relationship that is meaningful to themselves could make it difficult to find something that truly works for both of them.