If I love person A infinitely more than I love person B, I don't think it should matter that I love person B infinitely - there are orders of magnitude of infinity, you know. Although, I guess one could think that I only love person A twice as much as person B, but if the starting value is infinity, then twice as much is significantly more. Much more, say, than if I loved person A twice as much as person C, whom I may only love one tenth as much as I could. :)
Further, there is no upper limit to the amount we can love. I've never really given any credence the argument that there isn't enough room in one's "heart" to love only one person. How, then, do parents love their children equally? One could suggest that there is there a negative correlation between the number of children and the amount of love one has to give to each, or to a partner, but I don't buy it.
By the way, I certainly consider animals to be people (Thanks to my "God and Persons" class at Creighton University), although the lines between different classes of people are quite fuzzy and situation dependent.
Finally, it's best not to worry about it at all:
"Georg Cantor, who's responsible for much of the formal set theory that underlies these questions, went mad late in life and died in an asylum, as have some other people who have looked at them!"