Try giving your love bird some of the cockatiel food so he won't have to go looking for it. And he might just be lonely for a friend and enjoys sitting with your tiel. Birds from different species often make friends.

your lovebird is probably a female, when birds are "in heat" any birds company is enjoyed. if it were a male, they'd try to kill one another or just ignore each other altogether

Maybe there are opposite sexes and attracted to one another. Or just like each other's company. Like people do.

I dont know the gender of my lovebird, my cockatail is a male. I always find my lovebird in his cage and on top my lovebird likes to eat my cockatails food. The lovebird is always sneaking in there. I dont why?