PBS: Infant’s Emotional Milestones (And click on the image-link that says “ABC’s of Child Development” to see the physical, intellectual, and communicatory milestones as well.) Based on this checklist, I’d say he does and he has for at least a few months. (Birth-3 months, can be comforted by familiar adults, comforted by physical touch, can smile and show pleasure—understands and appreciates shows of affection.) Looked it up just to have some other source with a timeline to answer with. In the communication milestones, birth-3 months they already react to pitch, tone, intonation of voices. 3–6 months, exchange sounds, facial expressions, and gestures in a rudimentary conversation.
My gut response before checking a checklist was simply, of course he does. He hasn’t read Shakespeare yet, but no one is expecting him to have. He has an instinctual sense of love, and ten months experience with a family who loves him a great deal and shows this in various ways. One way is in kissing him goodnight, so this is one of the ways he understands love.